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  • 251.
    Pavlovic, Srdan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Andersson, Magnus
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Lantz, Jonas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Reduced Aerodynamic Drag for Truck-Trailer Configurations Using Parametrized CFD Studies2012In: ASME 2012 International Mechanical Engineering Congress and Exposition, Volume 7: Fluids and Heat Transfer Parts A, B, C, and D, New York, NY, USA: American Society of Mechanical Engineers , 2012, p. 1213-1220Conference paper (Refereed)
    Abstract [en]

    In the presented work, two studies using ComputationalFluid Dynamics (CFD) have been conducted on a generictruck-like model with and without a trailer unit at a speed of 80km/h. The purpose is to evaluate drag reduction possibilitiesusing externally fitted devices. A first study deals with a flapplaced at the back of a rigid truck and inclined at seven differentangles with two lengths. Results show that it is possible todecrease drag by 4%. In a second study, the flap has been fittedon the tractor and trailer units of a truck-trailer combination.Four settings were surveyed for this investigation, one of whichproved to decrease drag by up to 15%. A last configurationwhere the gap between the units has been closed has also beenevaluated. This configuration offers a 15% decrease in drag.Adding a flap to the closed gap configuration decreases drag by18%. New means of reducing aerodynamic drag of heavy-duty(HD) vehicles will be important in the foreseeable future inorder to improve the fuel economy. The possibilities of reducingdrag are prevalent using conceptual design.

  • 252.
    Pawa, Diptesh
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Greehouse Gas Simulations in Munich: Investigation of Wind Averaging Techniques for analysis of column measurements (XCO2) using CFD2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The underlying objective of this thesis was to perform GHG simulation studies to predict the dispersion and transport of greenhouse gases emitted from a thermal power plant in order to assess the extent of dangerous living environment for those surrounding it in case of an unforeseen calamity.

    The research carried out during this thesis was to investigate the method of wind averaging techniques to analyse column measurements (XCO2). The reason for adopting this method of analysis was to correlate the physical aspect of wind data to average over a certain period of time wherein the amount of XCO2 (in ppm) observed displays values greater than the background concentration.

    CFD simulations were performed using the open source code, OpenFOAM, and steady RANS models modified with turbulence boundary conditions for the urban environment case with previously validated simulation studies carried out for the same region in Munich, Germany.

    Initial results performed during the testing stage indicated that maximum average XCO2 value (in ppm) was recorded at the lowest value of mean wind speed and at a more downwind location of the measurement site. The results obtained from simulation studies on comparison with experimental values (arithmetic average) also suggest that for the same time interval, the difference in values for similar wind conditions as mentioned before makes this technique a more favourable choice for comparison and verification at another time instant. 

    There have been recent developments in GHG simulation based studies and however the current method does represent certain drawbacks, an insight into performing averaging analysis at time intervals representing peak XCO2 moments could be demonstrated which can also help in reducing the overall number of simulations as well as provide information with respect to mitigation measures based on transport and diffusion behavior.

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    greenhouse_gas_simulations_in_munich
  • 253.
    Pelosi, Matteo
    et al.
    Öhlins Racing AB, Jönköping, Sweden.
    Subramanya, Kashyap
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Lantz, Jonas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Investigation on the Dynamic Behavior of a Solenoid Hydraulic Valve for Automotive Semi-Active Suspensions Coupling 3D and 1D Modeling2013In: 13th Scandinavian International Conference on Fluid Power / [ed] Petter Krus, Magnus Sethson and Liselott Ericson, Linköping University Electronic Press, 2013, p. 241-250Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to investigate the influence of the internal fluid flow characteristics of a special hydraulic solenoid valve, developed by Öhlins Racing AB, on its overall dynamic behavior. This valve is a two stage hydraulic pressure control valve and is typically mounted on each shock absorber of an on-road vehicle, allowing the implementation of semi-active suspension functionality. This technology is referred as CES (Continuously Controlled Electronic Suspension). The CES valve allows continuously controlling the vehicle shock absorbers damping characteristic by proportionally adjusting the metering geometry offered to its damping element, i.e. hydraulic oil. The electronic valve actuation and control, obtained through an electromagnetic solenoid, is based on the input from several vehicle dynamics sensors, such as accelerometers, gyroscopes and other displacement sensors. The CES valve’s unconventional design significantly influences the fluid flow, making the use of numerical modeling essential to discover its physical behavior and to support further product development. In this paper, a CFD (Computational Fluid Dynamics) analysis on the main and pilot stages of the hydraulic valve is discussed. This 3D numerical analysis is used to extract critical physical variables, affecting the valve behavior, such as flow coefficients and pressure distributions on the moving elements, i.e. flow forces. This information is coupled with a detailed lumped parameter model of the hydraulic valve, which solves for the valve moving element dynamics considering the action of the main external forces. Moreover, the 1D model allows predicting the valve critical pressure/flow characteristics. It is shown how the coupling of 3D modeling results with the CES valve 1D model strongly improves the whole valve dynamics numerical predictions over traditional methods for considering the effect of fluid inertia and discharge in lumped parameter simulations. Comparisons with measurement both on single regions of the CES hydraulic valve and on the entire valve are discussed in order to validate the various phases of numerical modeling.

  • 254.
    Perez Sancha, David
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    CFD analysis of a glider aircraft: Using different RANS solvers and introducing improvements in the design2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this study, Computational Fluid Dynamics (CFD) simulations have been carried out in order to investigate and improve the performance of the Standard Cirrus glider, using different Navier-Stokes methods and solving the equations for the steady flow. The work has been divided in two parts:

    First, a study is performed to test the quality of the transition model (Gamma-ReTheta). The two dimensional results of the glider´s airfoil are compared against the results from panel’s methods and the open-source CFD codes: SU2 and OpenFoam. In addition, three dimensional glider´s models are simulated using the transition model with the purpose of creating a validated reference model of the glider’s performance in steady level flight. The simulations are carried out in two dimensions for the outer wing airfoil for a 1.5 e+06 Reynolds number and in three dimensions for the Wing & Fuselage model and Tail & Fuselage model under a range of velocities. Both simulations are validated against experimental data.

    In the second part of the study, the validated model is used to developed possible improvements in the glider´s external geometry that could produce possible benefits in the performance and handling qualities of the glider.

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    fulltext
  • 255.
    Petersson, Jens
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    CFD-analysis of buoyancy-driven flow inside a cooling pipe system attached to a reactor pressure vessel2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this work a cooling system connected to a reactor pressure vessel has been studied using the CFD method for the purpose of investigating the strengths and shortcomings of using CFD as a tool in similar fluid flow problems within nuclear power plants. The cooling system is used to transport water of 288K (15°C) into a nuclear reactor vessel filled with water of about 555K (282°C) during certain operating scenarios. After the system has been used, the warm water inside the vessel will be carried into the cooling system by buoyancy forces. It was of interest to investigate how quickly the warm water moves into the cooling system and how the temperature field of the water changes over time.

    Using the open source CFD code OpenFOAM 2.3.x and the LES turbulence modelling method, a certain operating scenario of the cooling system was simulated. A simplified computational domain was created to represent the geometries of the downcomer region within the reactor pressure vessel and the pipe structure of the cooling system. Boundary conditions and other domain properties were chosen and motivated to represent the real scenario as good as possible. For the geometry, four computational grids of different sizes and design were generated. Three of these were generated using the ANSA pre-processing tool, and they all have the same general structure only with different cell sizes. The fourth grid was made by the OpenFOAM application snappyHexMesh, which automatically creates the volume mesh with little user input.

    It was found that for the case at hand, the different computational grids produced roughly the same results despite the number of cells ranging from 0,14M to 3,2M. A major difference between the simulations was the maximum size of the time steps which ranged from 0,3ms for the finest ANSA mesh to 2ms for the snappy mesh, a difference which has a large impact on the total time consumption of the simulations.

    Furthermore, a comparison of the CFD results was made with those of a simpler 1D thermal hydraulic code, Relap5. The difference in time consumption between the two analyses were of course large and it was found that although the CFD analysis provided more detailed information about the flow field, the cheaper 1D analysis managed to capture the important phenomena for this particular case. However, it cannot be guaranteed that the 1D analysis is sufficient for all similar flow scenarios as it may not always be able to sufficiently capture phenomena such as thermal shocks and sharp temperature gradients in the fluid.

    Regardless of whether the CFD method or a simpler analysis is used, conservativeness in the flow simulation results needs to be ensured. If the simplifications introduced in the computational models cannot be proved to always give conservative results, the final simulation results need to be modified to ensure conservativeness although no such modifications were made in this work.

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    CFDBuoyancyDrivenFlow2014
  • 256.
    Petersson, Sven
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences.
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Simulation of phase contrast MRI of turbulent flow2010In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 64, no 4, p. 1039-1046Article in journal (Refereed)
    Abstract [en]

    Phase contrast MRI is a powerful tool for the assessment of blood flow. However, especially in the highly complex and turbulent flow that accompanies many cardiovascular diseases, phase contrast MRI may suffer from artifacts. Simulation of phase contrast MRI of turbulent flow could increase our understanding of phase contrast MRI artifacts in turbulent flows and facilitate the development of phase contrast MRI methods for the assessment of turbulent blood flow. We present a method for the simulation of phase contrast MRI measurements of turbulent flow. The method uses an Eulerian-Lagrangian approach, in which spin particle trajectories are computed from time-resolved large eddy simulations. The Bloch equations are solved for each spin for a frame of reference moving along the spins trajectory. The method was validated by comparison with phase contrast MRI measurements of velocity and intravoxel velocity standard deviation (IVSD) on a flow phantom consisting of a straight rigid pipe with a stenosis. Turbulence related artifacts, such as signal drop and ghosting, could be recognized in the measurements as well as in the simulations. The velocity and the IVSD obtained from the magnitude of the phase contrast MRI simulations agreed well with the measurements.

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    fulltext
  • 257.
    Pettersson, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Pettersson, Henrik
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Safety Evaluation of the Plunge Pool and the Downstream River of the Baihetan Hydropower Station Using Model Experiments2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a part of the hydropower expansion in China, the Baihetan Hydropower Station is now being constructed in the southern parts of the country. This hydropower station will, when completed, become the third largest in the world in terms of installed power output.The construction of a hydropower plant of the Baihetans Hydropower Station’s size is not without problems and high standards of safety are essential as large land areas upstream and downstream of the dam are affected. One of the risks is that the flow of water through the dam can cause scour and erosion downstream of the dam which threatens the stability of both the dam and the riverbed. To evaluate this risk, studies of a model in the scale of 1:100 have been performed at the Department of Hydraulic Engineering at Tsinghua University in Beijing, China.This thesis evaluates whether the discharge through the dam causes a hydrodynamic pressure above the allowed limit in the plunge pool below the dam and which measures that can be made to reduce this pressure. Flow velocity measurements were conducted, both in the plunge pool and along the downstream riverbed, to further evaluate the risk of erosion.The experiments show that the use of nappe splitters in two of the surface spillways will reduce the hydrodynamic pressure in the plunge pool to well below the acceptable limit of 15 m H2O. However, the flow velocity downstream of the plunge pool is too large and protection measures are recommended to avoid riverbed erosion.The results obtained indicate that a shortening of the plunge pool is possible which would lead to a reduced construction cost. However, further studies would be necessary to determine if this increases the risk of erosion in the downstream river.

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    Safety Evaluation of the Plunge Pool and the Downstream River of the Baihetan Hydropower Station Using Model Experiments
  • 258.
    Randell, Per
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Numerical Simulation of Temperature and Velocity Profiles in a Horizontal CVD-reactor2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Silicon Carbide (SiC) has the potential to significantly improve electronics. As a material, it can conduct heat better, carry larger currents and can give faster responses compared to today’s technologies. One way to produce SiC for use in electronics is by growing a thin layer in a CVD-reactor (chemical vapour deposition). A CVD-reactor leads a carrier gas with small parts of active gas into a heated chamber (susceptor). The gas is then rapidly heated to high temperatures and chemical reactions occur. These new chemical substances can then deposit on the substrate surface and grow a SiC layer. This thesis investigates the effect of different opening angles on a susceptor inlet in a SiC horizontal hot-walled CVD-reactor at Linköping University. The susceptor inlet affects both the flow and heat transfer and therefore has an impact on the conditions over the substrate. A fast temperature rise in the gas as close to the substrate as possible is desired. Even temperaturegradients vertically over the substrate and laminar flow is desired. The CVD-reactor is modeled with conjugate heat transfer using CFD simulations for three different angles of the inlet. The results show that the opening angle mainly affects the temperature gradient over the substrate and that a wider opening angle will cause a greater gradient. The opening angle will have little effect on the temperature of the satellite and substrate.

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    fulltext
  • 259. Order onlineBuy this publication >>
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Towards Subject Specific Aortic Wall Shear Stress: a combined CFD and MRI approach2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cardiovascular system is an important part of the human body since it transports both energy and oxygen to all cells throughout the body. Diseases in this system are often dangerous and cardiovascular diseases are the number one killer in the western world. Common cardiovascular diseases are heart attack and stroke, which origins from obstructed blood flow. It is generally important to understand the causes for these cardiovascular diseases. The main causes for these diseases are atherosclerosis development in the arteries (hardening and abnormal growth). This transform of the arterial wall is believed to be influenced by the mechanical load from the flowing blood on the artery and especially the tangential force the wall shear stress. To retrieve wall shear stress information in arteries invivo is highly interesting due to the coupling to atherosclerosis and indeed a challenge. The goal of this thesis is to develop, describe and evaluate an in-vivo method for subject specific wall shear stress estimations in the human aorta, the largest artery in the human body. The method uses an image based computational fluid dynamics approach in order to estimate the wall shear stress. To retrieve in-vivo geometrical descriptions of the aorta magnetic resonance imaging capabilities is used which creates image material describing the subject specific geometry of the aorta. Magnetic resonance imaging is also used to retrieve subject specific blood velocity information in the aorta. Both aortic geometry and velocity is gained at the same time. Thereafter the image material is interpreted using level-set segmentation in order to get a three-dimensional description of the aorta. Computational fluid dynamics simulations is applied on the subject specific aorta in order to calculate time resolved wall shear stress distribution at the entire aortic wall included in the actual model.

    This work shows that it is possible to estimate subject specific wall shear stress in the human aorta. The results from a group of healthy volunteers revealed that the arterial geometry is very subject specific and the different wall shear stress distributions have general similarities but the level and local distribution are clearly different. Sensitivity (on wall shear stress) to image modality, the different segmentation methods and different inlet velocity profiles have been tested, which resulted in these general conclusions:

    • The aortic diameter from magnetic resonance imaging became similar to the reference diameter measurement method.
    • The fast semi-automatic level-set segmentation method gave similar geometry and wall shear stress results when compared to a reference segmentation method.
    • Wall shear stress distribution became different when comparing a simplified uniform velocity profile inlet boundary condition with a measured velocity profile.

    The method proposed in this thesis has the possibility to produce subject specific wall shear stress distribution in the human aorta. The method can be used for further medical research regarding atherosclerosis development and has the possibility for usage in clinical work.

    List of papers
    1. Subject Specific Wall Shear Stress in the Human Thoracic Aorta
    Open this publication in new window or tab >>Subject Specific Wall Shear Stress in the Human Thoracic Aorta
    2006 (English)In: WSEAS Transaction on biology and biomedicine, ISSN 1109-9518, Vol. 10, no 3, p. 609-614Article in journal (Refereed) Published
    Abstract [en]

    Numerous studies have shown a correlation between Wall Shear Stress (WSS) and atherosclerosis, but few have evaluated the reliability of estimation methods and measures used to assessWSS, which is the subject of this work. A subject specific vessel model of the aortic arch and thoracic aorta is created fromMRI images and used for CFD simulations with MRI velocity measurements as inlet boundary condition. WSS is computed from the simulation results. Aortic WSS shows significant spatial as well as temporal variation during a cardiac cycle, which makes circumferential values very uninformative, and approximate estimates using Hagen-Poiseuille fails predict the averageWSS. Highly asymmetric flow, especially in the arch, causes the spatial WSS variations.

    Keywords
    Wall shear stress, CFD, Aorta, Circumferential average values, Asymmetric flow
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-43727 (URN)74619 (Local ID)74619 (Archive number)74619 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27Bibliographically approved
    2. Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Open this publication in new window or tab >>Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Show others...
    2006 (English)In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006: 9th International Conference, Copenhagen, Denmark, October 1-6, 2006. Proceedings, Part I / [ed] Rasmus Larsen, Mads Nielsen and Jon Sporring, Springer Berlin/Heidelberg, 2006, 1, Vol. 4190, p. 257-263Conference paper, Published paper (Refereed)
    Abstract [en]

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2006 Edition: 1
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 4190
    National Category
    Medical Image Processing
    Identifiers
    urn:nbn:se:liu:diva-36902 (URN)10.1007/11866565_32 (DOI)000241556300032 ()32988 (Local ID)3-5404-4707-5 (ISBN)978-3-540-44727-6 (ISBN)978-3-540-44707-8 (ISBN)32988 (Archive number)32988 (OAI)
    Conference
    The 9th MICCAI Conference, Copenhagen, Denmark, 1-6 October 2006
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-02-20Bibliographically approved
    3. Evaluation of Aortic Geometries created by MRI Data in Man
    Open this publication in new window or tab >>Evaluation of Aortic Geometries created by MRI Data in Man
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    2011 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 31, no 6, p. 485-491Article in journal (Refereed) Published
    Abstract [en]

    The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in man based on data from magnetic resonance imaging (MRI) with ultrasound as reference.

    Methods: The aortas of ten healthy males, 23.4 ± 1.6 years of age, were examined with MRI, and 3D geometries were created with manual segmentation of the images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non-invasive B-mode ultrasound as a reference.

    Results: The anteroposterior diameter of the AA was 13.6 ± 1.1 mm for the MRI and 13.8 ± 1.3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0.92% and <0.40% respectively . Interobserver variability MRI and ultrasound was 0.96% and 0.56% respectively. The diameter of the TA was 19.2 ± 1.4 mm for the MRI, and the intraobserver variability (CV) were <0.78% and interobserver variability (CV) were 0.92%.

    Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicate that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of man.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2011
    Keywords
    human aorta, lumen diameter, magnetic resonance imaging, manual segmentation, ultrasound
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-65905 (URN)10.1111/j.1475-097X.2011.01035.x (DOI)000296198100011 ()
    Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-12-11Bibliographically approved
    4. Wall Shear Stress Estimations using Semi-Automatic Segmentation
    Open this publication in new window or tab >>Wall Shear Stress Estimations using Semi-Automatic Segmentation
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such entity in-vivo in humans, is image based computational fluid dynamics (CFD) a powerful tool. In this paper we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method a number of steps is included. One important step is the image interpretation into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparingWSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of 8 healthymale volunteers. The different segmentation methods give slightly different geometrical descriptions of the human aorta. However there is a very good agreement between the resultingWSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time position indicating that theWSS is more sensitive to local geometry differences in these parts of the cardiac cycle. We can conclude that the results show that the semi-automatic segmentation method can be used in the future to estimate WSS with relevant accuracy.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-65906 (URN)
    Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-03-27Bibliographically approved
    5. A method for subject specific estimation of aortic wall shear stress
    Open this publication in new window or tab >>A method for subject specific estimation of aortic wall shear stress
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    2009 (English)In: WSEAS Transactions on Biology and Biomedicine, ISSN 1109-9518, Vol. 6, no 3, p. 49-57Article in journal (Refereed) Published
    Abstract [en]

    Wall shear stress (WSS) distribution in the human aorta is a highly interesting hemodynamic factor for atherosclerosis development. We present a magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) based subject specific WSS estimation method and demonstrate it on a group of nine healthy volunteers (males age 23.6 ± 1.3 years). In all nine subjects, the aortic blood flow was simulated in a subject specific way, where the 3D segmented geometries and inflow profiles were obtained using MRI. No parameter settings were tailored using data from the nine subjects. Validation was performed by comparing CFD gained velocity with magnetic resonance imaging (MRI) velocity measurements. CFD and MRI velocity profiles were comparable, but the temporal variations of the differences during the cardiac cycle were significant. Spatio-temporal analyzes on the WSS distribution showed a strong subject specific influence. Subject specific models are decisive to estimate WSS distribution.

    Place, publisher, year, edition, pages
    WSEAS Press, 2009
    Keywords
    3D segmentation; Aorta; CFD; MRI; Subject specific; Velocity validation; WSS
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-57056 (URN)
    Available from: 2010-06-11 Created: 2010-06-09 Last updated: 2017-03-27Bibliographically approved
    6. Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
    Open this publication in new window or tab >>Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
    2009 (English)In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 4, p. 148-160Article in journal (Refereed) Published
    Abstract [en]

    Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

    Keywords
    Aorta; CFD; Inlet boundary condition; Subject specific; Uniform velocity profile; Wall shear stress
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-53002 (URN)
    Available from: 2010-01-14 Created: 2010-01-14 Last updated: 2017-03-27Bibliographically approved
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    Towards Subject Specific Aortic Wall Shear Stress : a combined CFD and MRI approach
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    COVER01
  • 260.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Using Industrial Projects in a Heat Transfer Course for Engineering Students2011Conference paper (Other (popular science, discussion, etc.))
  • 261.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Andersson, Magnus
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Storck, Karl
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Ekman, Petter
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Real-world Engineering Projects in a Master Level Course2016In: Proceedings of the International CDIO Conference, 2016Conference paper (Other academic)
    Abstract [en]

    Real-world engineering projects are problems supplied by industry or institutions that is not primarily intended only as an educational exercise but are rooted in a relevant engineering issue. These projects are incorporated as an important part of a six ECTS-credits master course in computational heat-transfer. Normally 70-80 students attend the course and are typically allowed to choose among four to five different projects. Overall impression is that the inclusion of these engineering problems results in higher level of questions, skills and motivation of the students.

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  • 262.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ghavami Nejad, Mehdi
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Skoog, Pontus
    SAPA Heat Transfer AB.
    Abrahamsson, David
    SAPA Heat Transfer AB.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Conduction and convection heat transfer for aluminum ingot in preheating furnace2011In: Proceedings of 6th Baltic Heat Transfer Conference 2011 / [ed] Reijo Karvinen & Matti Lindstedt, 2011Conference paper (Refereed)
    Abstract [en]

    Aluminium is a widely used material, which is found in a number of products e.g. thin aluminium bands that is the base material in many heat exchangers. Rolling processes are used to produce these thin aluminium bands, in order to get the right properties and to get the aluminium easier to roll, heat treatment is needed. This heat treatment of aluminium ingots prior to the rolling is in focus in this work, where computational fluid dynamics and computational heat transfer techniques is used to predict the heating process in a hot air pre-heating furnace. The used approach includes steady state computational fluid dynamics simulations combined with transient computational heat transfer simulations. The simulation results in form of spatial and temporal distributed aluminium ingot temperature was compared with temperature measurement in a thermocouple prepared ingot in the actual pre-heating furnace. Simulation results correspond well with the measurements and there are small differences. Results of the described simulation approach open the possibility to predict spatial and temporal temperature distribution in these kinds of pre-heating processes.

  • 263.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Department of Medicine and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Heiberg, Einar
    Department of Clinical Physiology, Lund University Hospital, Sweden.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    A method for subject specific estimation of aortic wall shear stress2009In: WSEAS Transactions on Biology and Biomedicine, ISSN 1109-9518, Vol. 6, no 3, p. 49-57Article in journal (Refereed)
    Abstract [en]

    Wall shear stress (WSS) distribution in the human aorta is a highly interesting hemodynamic factor for atherosclerosis development. We present a magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) based subject specific WSS estimation method and demonstrate it on a group of nine healthy volunteers (males age 23.6 ± 1.3 years). In all nine subjects, the aortic blood flow was simulated in a subject specific way, where the 3D segmented geometries and inflow profiles were obtained using MRI. No parameter settings were tailored using data from the nine subjects. Validation was performed by comparing CFD gained velocity with magnetic resonance imaging (MRI) velocity measurements. CFD and MRI velocity profiles were comparable, but the temporal variations of the differences during the cardiac cycle were significant. Spatio-temporal analyzes on the WSS distribution showed a strong subject specific influence. Subject specific models are decisive to estimate WSS distribution.

  • 264.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Subject Specific In-Vivo CFD Estimated Aortic WSS: Comparison Between Manual and Automated Segmentation Methods2009In: ASME 2008 Summer Bioengineering Conference: Parts A and B, The American Society of Mechanical Engineers (ASME) , 2009, no PART A, p. 425-426Conference paper (Refereed)
    Abstract [en]

    When making computational fluid dynamics (CFD) based estimations of wall shear stress (WSS) in the human aorta, medical image converting processes to 3D geometries are important as the result is strongly dependent on the quality of the geometry [1]. The image interpretation process or segmentation can be more or less automated; however in clinical work today the gold standard is to manually interpret the medical image information. This combined magnetic resonance imaging (MRI) and CFD method aims to estimate WSS in human arteries in-vivo as WSS is strongly linked to atherosclerosis [2]. More or less automated segmentation has been used in previous studies but normally based on a stack of 2D individually segmented slices which is combined into a 3D model [3]. The aim of this work is to compare manual 2D and automatic 3D segmentations.

  • 265.
    Renner, Johan
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Lantz, Jonas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Länne, Toste
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Karlsson, Matts
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Altered WSS in the human aorta with age – implications for wall remodeling and lesions?2012Conference paper (Other academic)
  • 266.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Is a flat inlet profile sufficient for WSS estimation in the aortic arch?2009In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 4, p. 148-160Article in journal (Refereed)
    Abstract [en]

    Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

  • 267.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Subject-specific aortic wall shear stress estimations using semi-automatic segmentation2012In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 6, p. 481-491Article in journal (Refereed)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such an entity in-vivo in humans, image-based computational fluid dynamics (CFD) is a useful tool. In this study, we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method, a number of steps are included. One important step is the interpretation of images into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparing WSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of eight healthy male volunteers. The different segmentation methods give slightly different geometrical depictions of the human aorta (difference in the mean thoracic Aorta lumen diameter were 0.7% Pandlt;0.86). However, there is a very good agreement between the resulting WSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time point indicating that the WSS is more sensitive to local geometric differences in these parts of the cardiac cycle (correlation coefficient is 0.96 at peak systole and 0.68 at early diastole). We can conclude that the results show that the semi-automatic segmentation method can be used in future to estimate relevant aortic WSS.

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  • 268.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Wall Shear Stress Estimations using Semi-Automatic SegmentationManuscript (preprint) (Other academic)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such entity in-vivo in humans, is image based computational fluid dynamics (CFD) a powerful tool. In this paper we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method a number of steps is included. One important step is the image interpretation into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparingWSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of 8 healthymale volunteers. The different segmentation methods give slightly different geometrical descriptions of the human aorta. However there is a very good agreement between the resultingWSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time position indicating that theWSS is more sensitive to local geometry differences in these parts of the cardiac cycle. We can conclude that the results show that the semi-automatic segmentation method can be used in the future to estimate WSS with relevant accuracy.

  • 269.
    Rolf, Marijn P
    et al.
    Vrije University Amsterdam Medical Centre.
    Hofman, Mark B M
    Vrije University Amsterdam Medical Centre.
    Gatehouse, Pete rD
    Royal Brompton Hospital.
    Markenroth-Bloch, Karin
    Skane University Hospital.
    Heymans, Martijn W
    Vrije University Amsterdam Medical Centre.
    Ebbers, Tino
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Graves, Martin J
    Cambridge University Hospital.
    Totman, John J
    Kings College London.
    Werner, Beat
    University Childrens Hospital.
    van Rossum, Albert C
    Vrije University Amsterdam Medical Centre.
    Kilner, Philip J
    Royal Brompton Hospital.
    Heethaar, Rob M
    Vrije University Amsterdam Medical Centre.
    Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification - A multi-vendor study2011In: JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, ISSN 1097-6647, Vol. 13Article in journal (Refereed)
    Abstract [en]

    Purpose: Eddy current induced velocity offsets are of concern for accuracy in cardiovascular magnetic resonance (CMR) volume flow quantification. However, currently known theoretical aspects of eddy current behavior have not led to effective guidelines for the optimization of flow quantification sequences. This study is aimed at identifying correlations between protocol parameters and the resulting velocity error in clinical CMR flow measurements in a multi-vendor study. Methods: Nine 1.5T scanners of three different types/vendors were studied. Measurements were performed on a large stationary phantom. Starting from a clinical breath-hold flow protocol, several protocol parameters were varied. Acquisitions were made in three clinically relevant orientations. Additionally, a time delay between the bipolar gradient and read-out, asymmetric versus symmetric velocity encoding, and gradient amplitude and slew rate were studied in adapted sequences as exploratory measurements beyond the protocol. Image analysis determined the worst-case offset for a typical great-vessel flow measurement. Results: The results showed a great variation in offset behavior among scanners (standard deviation among samples of 0.3, 0.4, and 0.9 cm/s for the three different scanner types), even for small changes in the protocol. Considering the absolute values, none of the tested protocol settings consistently reduced the velocity offsets below the critical level of 0.6 cm/s neither for all three orientations nor for all three scanner types. Using multilevel linear model analysis, oblique aortic and pulmonary slices showed systematic higher offsets than the transverse aortic slices (oblique aortic 0.6 cm/s, and pulmonary 1.8 cm/s higher than transverse aortic). The exploratory measurements beyond the protocol yielded some new leads for further sequence development towards reduction of velocity offsets; however those protocols were not always compatible with the time-constraints of breath-hold imaging and flow-related artefacts. Conclusions: This study showed that with current systems there was no generic protocol which resulted into acceptable flow offset values. Protocol optimization would have to be performed on a per scanner and per protocol basis. Proper optimization might make accurate (transverse) aortic flow quantification possible for most scanners. Pulmonary flow quantification would still need further (offline) correction.

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  • 270.
    Romanov, Artyom
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University. Linköping University, Department of Management and Engineering.
    Rocket Engine System Analysis: Vinci Engine Turbines Analysis, Volvo Aero Corp.2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Major part of the current work describes the development of the update methodology for onedimensional code (TML) currently used at Volvo Aero Corporation during turbine design process. The methodology is then applied and tried out in a general engine analysis (GESTPAN).

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  • 271.
    Sadrizadeh, Sasan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Instabilities in Pulsating Pipe Flow of Shear-Thinning and Shear-Thickening Fluids2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study, we have considered the modal and non-modal stability of fluids with shear-dependent viscosity flowing in a rigid straight pipe. A second order finite-difference code is used for the simulation of pipe flow in the cylindrical coordinate system. The Carreau-Yasuda model where the rheological parameters vary in the range of 0.3 < n < 1.5 and 0.1 < λ < 100 is represents the viscosity of shear- thinning and shear thickening fluids. Variation of the periodic pulsatile forcing is obtained via the ratio Kω/Kο and set between 0.2 and 20. Zero and non-zero streamwise wavenumber have been considered separately in this study.

    For the axially invariant mode, energy growth maxima occur for unity azimuthal wave number, whereas for the axially non-invariant mode, maximum energy growth can be observed for azimuthal wave number of two for both Newtonian and non-Newtonian fluids. Modal and non-modal analysis for both Newtonian and non-Newtonian fluids show that the flow is asymptotically stable for any configuration and the pulsatile flow is slightly more stable than steady flow. Increasing the maximum velocity for shear-thinning fluids caused by reducing power-low index n is more evident than shear-thickening fluids. Moreover, rheological parameters of Carreau-Yasuda model have ignored the effect on the peak velocity of the oscillatory components. Increasing Reynolds number will enhance the maximum energy growth while a revers behavior is observed by increasing Womersley number.

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    Instabilities in pulsating pipe flow
  • 272.
    Safaric, Luka
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Biogas Research Center.
    Shakeri Yekta, Sepehr
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Biogas Research Center.
    Ejlertsson, Jörgen
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Biogas Research Center. Scandinavian Biogas Fuels AB.
    Safari, Mohammad
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Karlsson, Anna
    Linköping University, Biogas Research Center. Scandinavian Biogas Fuels AB.
    Ometto, Francesco
    Linköping University, Biogas Research Center. Scandinavian Biogas Fuels AB.
    Svensson, Bo H
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Björn, Annika
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Biogas Research Center.
    A Comparative Study of Biogas Reactor Fluid Rheology: Implications for Mixing Profile and Power Demand2019In: Processes, ISSN 2227-9717, Processes, ISSN 2227-9717, Vol. 7, no 10Article in journal (Refereed)
    Abstract [en]

    Anaerobic digestion (AD) is an established process for integrating waste management with renewable energy and nutrient recovery. Much of the research in this field focuses on the utilisation of new substrates, yet their effects on operational aspects such as fluid behaviour and power requirement for mixing are commonly overlooked, despite their importance for process optimisation. This study analysed rheological characteristics of samples from 21 laboratory-scale continuous stirred-tank biogas reactors (CSTBRs) digesting a range of substrates, in order to evaluate substrate effect on mixing efficiency and power demand through computational fluid dynamics (CFD). The results show that substrate and process parameters, such as solids content and organic loading, all have a significant effect on CSTBR fluid rheology. The correlation levels between rheological and process parameters were different across substrates, while no specific fluid behaviour patterns could be associated with substrate choice. Substrate should thus be considered an equally important rheology effector as process parameters. Additional substrate-related parameters should be identified to explain the differences in correlations between rheological and process parameters across substrate groups. The CFD modelling revealed that the rheology differences among the AD processes have significant implications for mixing efficiency and power demand of the CSTBRs, highlighting the importance of considering the substrate-induced effects on CSTBR rheology before including a new substrate.

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  • 273.
    Safavi, Edris
    et al.
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, Faculty of Science & Engineering.
    Tarkian, Mehdi
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, Faculty of Science & Engineering.
    Ölvander, Johan
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, Faculty of Science & Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Munjulury, Raghu Chaitanya
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Implementation of collaborative multidisciplinary design optimization for conceptual design of a complex engineering product2016In: Concurrent Engineering - Research and Applications, ISSN 1063-293X, E-ISSN 1531-2003, Vol. 24, no 3, p. 251-265Article in journal (Refereed)
    Abstract [en]

    This study investigates the performance of the collaborative multidisciplinary design optimization framework and how it facilitates the knowledge integration process. The framework is used to design and optimize an innovative concept of a tidal water power plant. The case study helps to highlight the challenges that may occur during implementation. The result is presented as a modified framework with less implementation difficulties. The improved framework shows significant reduction in design time and improvement in collaborative design optimization for a design team. The geometry of the product is optimized to minimize weight and maximize the power generated by the turbine with respect to some mechanical constraints.

  • 274.
    Sammartano, Chiara
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Simulation of radio-frequency ablation of liver tumors: Development of a power regulation model and comparison with microwave ablation2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Local therapy with radiofrequency ablation (RFA) is an important method for treating liver tumors mostly in early stage, which has been increasingly used in recent years.

    RFA utilizes an RF current that is applied to the target tissue through an electrode connected with a power generator and percutaneously inserted into the tumor; the electrode power causes the tissue temperature rise required for destroying cancer cells.

    If RF thermal ablation entails numerous advantages - such as high repeatability of treatments, suitability for patients who can‟t undergo surgery, quick procedure and fast recovery -, there are still some inconveniences and difficulties coupled with this technique. One of these problems is the so called heat sink effects, resulting from the presence of large blood vessels close to the electrode tip.

    First, an overview is given of RFA physical background and heat transfer models followed by the improvement of a model of RF ablation in the liver. Second, special attention has been given to the mesh settings so that the simulation model could benefit from an appropriate mesh in terms of resolution and accuracy of the results obtained and in terms of reduced computational time. Then, a large part of the work has been dedicated to the development of a power regulation (PR) aiming at an optimization of the thermal treatment although the presence of large blood vessels in the ablation area and at an abatement of the number of residual tumors. Finally, a comparison work has been conducted between two different ablation modalities (RF versus MW) showing similarities and differences until the conclusion that currently the RFA treatment is the most suitable treatment for tumors in early stage, small and localized.

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  • 275.
    Samuelsson, Henrik
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    CFD Modeling and Design of an Air Heater Mixing System in a Gypsum Board Dryer2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The process of manufacturing gypsum boards in a Gyptech gypsum plant involves, among other things, drying of the boards to remove excess water. It is here crucial that the drying occurs uniformly over the boards, as the gypsum properties and consequently the quality of the end product relies on it. Uniform drying can be ensured by having a uniform temperature of the air ejected over the gypsum boards, which in turn is facilitated by having a static mixer in the air heater channel.

    In the present work, the air heater channel has been modeled using Computational Fluid Dynamics (CFD) and the purpose has been to improve the mixing capabilities of the static mixer while a low pressure drop is maintained. A large portion of the work was spent on reducing and developing an appropriate domain that could be afforded given the large size of the dryer, the steep temperature gradients therein, and the relatively limited computer resources. The final model was compared to experiments, where the pressure drop was in good agreement; 89 Pa compared to the measured value of 100 Pa. The standard deviation in temperature was overpredicted however, something that is considered to be due to the domain simplifications and due to the use of steady state Reynolds-Averaged Navier-Stokes turbulence modeling.

    Two unsuccessful attempts of improving the static mixer included variations of some parameters of the current mixer and utilizing a second mixer downstream of the first. Other but entirely different concepts proved to be more promising; one including a variant of the corrugated plate mixer, one based on guide vanes, and one that was a modified version of the original static mixer. These reduced the standard deviation in reference to the original mixer in the CFD model by 68%, 13.8% and 22.9% respectively, and produced only moderate pressure drops. The results have shown the potential of some concepts, and have indicated that more large scale rearrangement and large scale vortices may achieve better mixing, in comparison to the original mixer. However, it can not be claimed that the optimal dimensions have been established for any of the concepts, as the number of cases that have been examined are limited.

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  • 276.
    Sanchez Abad, Nour
    et al.
    Royal Inst Technol, Sweden.
    Vinuesa, Ricardo
    Royal Inst Technol, Sweden.
    Schlatter, Philipp
    Royal Inst Technol, Sweden.
    Andersson, Magnus
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simulation strategies for the Food and Drug Administration nozzle using Nek50002020In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, AIP ADVANCES, Vol. 10, no 2, article id 025033Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics (CFD) is currently a versatile tool used for flow characterization in diverse areas of industry and research; however, its application in medical devices is less developed due to high regulatory standards for safety purposes. In this context, the development of a rigorous and standardized CFD methodology is essential in order to improve the accuracy and ensure the reliability of biomedical applications. To that end, the Food and Drug Administration (FDA) proposed a benchmark model of an idealized medical device to provide a common ground for verification and validation processes. Previous studies have evaluated the potential of conventional turbulence models to predict the relevant flow features in the FDA nozzle but have also been deemed inaccurate or exhibited high dependency on the numerical scheme. Furthermore, validation of computational results relied on previous experiments performed with particle image velocimetry (PIV), which also exhibited noticeable uncertainties. Here, we perform direct numerical simulations (DNSs) of the flow through the FDA nozzle configuration, at Reynolds numbers based on the throat diameter Re-t = 500, 2000, 3500, and 5000, using the spectral-element code Nek5000. The predictive capabilities of the synthetic-eddy method and parabolic-inflow conditions at the inlet were tested, and the results were compared with PIV data. Our results highlight the very high sensitivity of this flow case to the inflow conditions and the disturbances at the throat, particularly when predicting the laminar-turbulent jet breakdown. Due to this extreme sensitivity, any benchmark data of this geometry need to include a very detailed characterization of both the conditions at the inflow and the throat, in order to enable relevant comparisons.

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  • 277.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    A generic simulation model for prediction of thermal conditions and human performance in cockpits2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 143, p. 120-129Article in journal (Refereed)
    Abstract [en]

    This paper presents a computational approach to predict the thermal environment in a cockpit during on-ground and in-flight aircraft operation. A method was developed to model cockpit air temperature, which serves as input to black-globe and wet-bulb temperature computation. Subsequently the simulated temperatures are used to compute common heat stress indices such as Wet Bulb Globe Temperature (WBGT), Fighter Index of Thermal Stress (FITS), or Predicted Mean Vote (PMV). To demonstrate the manifold information made available by the computed heat stress indices, WBGT e.g. is set in relation to different types of occupational exposure limits demonstrating not only the possibility to predict physiological constraints but mental performance too. The generic cockpit model and thermal comfort computations were validated against experimental data gained from on ground temperature measurements inside an aircraft cockpit, which underwent a sudden large temperature change. The results exemplify how thermal comfort and possible physical as well as mental degradation of aircrews can be assessed quickly using the presented model.

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  • 278.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Nilsson, Elias
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Storck, Karl
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. SAAB Dynamics AB, Linköping, Sweden.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Development of a Cockpit-Pilot Model for Thermal Comfort Optimization During Long-Mission Flight2016In: AIAA Modeling and Simulation Technologies Conference San Diego, California, USA, AAAI Press, 2016Conference paper (Refereed)
    Abstract [en]

    The thermal comfort of a pilot is of crucial importance to maintain a high level ofconcentration and awareness during the entire ight mission. In this work a model for thethermal environment of the cockpit is developed and used as provider of input parametersto a thermoregulatory model, adopted from the literature, of a human. The cockpit-pilotmodel will be used to investigate and improve the thermal comfort for the pilot, particularlyduring longer ight missions. In the cockpit model a combination of lumped systems and nite dierence calculationsis used to obtain input parameters, which are provided to the pilot model. The body, withclothes, is divided into 16 segments and a nite dierence method is used to determine thetemperature distribution within these. Several physiological mechanisms are included inthe model. Simulations with dierent boundary conditions show that the models work properlyeven for longer missions.

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  • 279.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Hällqvist, Robert
    Systems Simulation and Concept Design, Saab Aeronautics, Linköping, Sweden.
    Eek, Magnus
    Systems Simulation and Concept Design, Saab Aeronautics, Linköping, Sweden.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    PILOT PERFORMANCE AND HEAT STRESS ASSESSMENT SUPPORT USING A COCKPIT THERMOREGULATORY SIMULATION MODEL2018In: ICAS congress proceeding, International Council of the Aeronautical Sciences , 2018, article id ICAS2018_0463Conference paper (Other academic)
    Abstract [en]

    Flights with high thermal loads inside the cockpit can have a considerable impact on pilot physiological and psychological performance resulting in thermal discomfort, dehydration and fatigue. In this work, a Functional Mock-up Interface (FMI) based aircraft system simulator is utilized with intent to compute and predict thermal comfort. The simulator can for example serve pilots as a tool for heat stress and flight risk assessment, supporting their pre-flight planning or be used by engineers to design and optimize cooling efficiency during an early aircraft design phase. Furthermore, the presented simulator offers several advantages such as map based thermal comfort analysis for a complete flight envelop, time resolved mental performance prediction, and a flexible composability of the included models.

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  • 280.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Learning by teaching: Student developed material for self-directed studies2016In: The 12th International CDIO Conference: Proceedings - Full Papers, Turku: Turku University of Applied Sciences , 2016, p. 750-759Conference paper (Refereed)
    Abstract [en]

    The objective of the presented paper is to demonstrate how e-learning course material developed by the students can enhance active learning for self-directed studies outside the classroom in a flipped classroom concept. A method which merges different learning activities such as learning by teaching, video based teaching etc. was developed to improve the students’ personal and interpersonal engineering skills in relation to CDIO standards. In an effort to assess the students’ satisfaction and practical use of the students’ created material, a survey was conducted. Statistics, the students’ feedback, and observations show an increase in learning motivation, deepened understanding, and expanded communication skills.

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  • 281.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Nilsson, Filip
    Linköping University.
    Lundberg, Paulina
    Linköping University.
    Nguyen, Nghiem-Anh
    Linköping University.
    Hag, Christoffer
    Linköping University.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    An IVR Engineering Educational Laboratory Accommodating CDIO Standards2019In: The 15th International CDIO Conference: Proceedings – Full Papers, Aarhus, 2019, p. 647-658Conference paper (Refereed)
    Abstract [en]

    This paper presents the development of an educational immersive virtual reality (IVR) program considering both technological and pedagogical affordances of such learning environments. The CDIO Standards have been used as guidelines to ensure desirable outcomes of IVR for an engineering course. A learning model has been followed to use VR characteristics and learning affordances in teaching basic principles. Different game modes, considered as learning activities, are incorporated to benefit from experiential and spatial knowledge representation and to create a learning experience that fulfils intended learning outcomes (ILOs) (defined by CDIO Standard 2 and Bloom’s learning taxonomy) associated with the particular course moment. The evaluation of IVR laboratory highlights effectiveness of the approach in achieving ILOs provided that pedagogical models have been followed to create powerful modes of learning.

  • 282.
    Schminder, Jörg
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Didacticum.
    Nilsson, Filip
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Lundberg, Paulina
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Nguyen, Nghiem-Ann
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Hag, Christoffer
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Didacticum.
    An IVR Engineering Educational Laboratory AccommodatingCDIO Standards2019In: The 15th International CDIO Conference: Proceedings – Full Papers, Aarhus, 2019Conference paper (Refereed)
    Abstract [en]

    This paper presents the development of an educational immersive virtual reality (IVR) program considering both technological and pedagogical affordances of such learning environments. The CDIO Standards have been used as guidelines to ensure desirable outcomes of IVR for an engineering course. A learning model has been followed to use VR characteristics and learning affordances in teaching basic principles. Different game modes, considered as learning activities, are incorporated to benefit from experiential and spatial knowledge representation and to create a learning experience that fulfils intended learning outcomes (ILOs) (defined by CDIO Standard 2 and Bloom’s learning taxonomy) associated with the particular course moment. The evaluation of IVR laboratory highlights effectiveness of the approach in achieving ILOs provided that pedagogical models have been followed to create powerful modes of learning.

  • 283.
    Schminder, Jörg Paul Wilhelm
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Feasibility study of different methods for the use in aircraft conceptual design2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    The comparison of aerodynamic characteristics for a combat aircraft studywas addressed in this work. The thesis is a feasibility study which reviewsthe workload and output quality efficiency of different numerical and experimentalmethods often used during conceptual aircraft design.For this reason the Vortex Lattice Method (VLM), Euler or Reynolds-Averaged-Navier-Stokes (RANS) simulations were compared to the moreheavier Large Eddy Simulation (LES) which also has the capability to capturealso more complex flow physics, such as those that occur, for example,at high angles of attack. To be able to crosscheck the numerical results,the same static alpha sweep tests were executed in a tunnel. Thereby itwas discovered that it was quite challenging to reach the same values in thewater tunnel as those previously calculated in computational fluid dynamics(CFD) due to different technical issues.However it could be shown that LES simulations can be today a suitabletool for conceptual aircraft design, as they offer much higher levels ofaccuracy and give the designer the possibility to check the new study at anearly stage along the border of the aircraft’s flight envelope.

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  • 284.
    Shetty, Neeti
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Multidisciplinary design Optimization in Aerodynamics and Aeroacoustics: Analysis of the A-Pillar2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A roof above your head, when in a car, is made possible due to the component calledthe A-pillar in the automotive industry. This component is not only responsible forholding up the roof but also in providing a point for the windscreen to be attached.Hence, it is denitely a part that can not be done away with and any problems arising from it must be solved. The flow over the A-pillar causes formation of vortices which causes an increase in the drag generated by the vehicle. These vortices also cause a high level of noise to be generated, which can cause discomfort inside the vehicle, when it is in motion. Hence, there is a need in the automotive industry to modify the A-pillar so as to reduce the generated drag and noise caused by it.

    In this thesis, the flow around the A-pillar is analyzed and modications are made accordingly to reduce the impact of the vortices formed due to it. The final resulting design of the A-pillar which has been modied from the aerodynamics and aeroacoustics point of view has been presented. This thesis project also includes the optimization of the method used to implement this. The method involved in obtaining an optimized design of the A-pillar started with the geometry cleaning phase in ANSA, followed by the meshing and simulation phase in FLUENT and finally concluding with the optimization phase in HEEDS. The process of doing this methodology has now been optimized resulting in lesser times between the models being cleaned and optimized.

    The baseline model obtained from these simulations has been validated by comparing the flow around the vehicle to other works and literature studies. This was done to be certain that the optimization method works to provide correct and accurate results. The optimized design, which called for an increased height was then compared against the baseline model, to understand the flow behavior that lead to the reduction of the output variables.

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  • 285.
    Simonsson, Kjell
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Hallberg, Peter
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Simonsson, Maria
    Linköping University, Department of Social and Welfare Studies, Learning, Aesthetics, Natural science. Linköping University, The Institute of Technology.
    Kamratutvärdering i kurser med stort datorlaborativt inslag2014Report (Other academic)
    Abstract [sv]

    De mångfacetterade krav som idag ställs på yrkesverksamma högskole- och civilingenjörer handlar inte enbart om rena ämnesmässiga kunskaper och förmågor, utan även om t.ex. erfarenhet och förmåga att delta i och leda projekt samt (kopplat till detta) kommunikativ skicklighet (såväl muntlig som skriftlig). En annan uppgift som yrkesverksamma ingenjörer måste kunna bemästra i sin profession är att (individuellt, eller som medlemmar i olika typer av styrgrupper) bedöma och utvärdera andras ingenjörsmässiga arbete, en oerhört central uppgift i ett projekt- och kvalitetssäkringsperspektiv.

    Det övergripande syftet med arbetet har varit att studera hur kamratbedömning kan implementeras i redan existerande kurser, för att på så sätt ge de studerande möjlighet att träna på att ge och ta emot kritisk bedömning, att förbättra de studerandes lärande via ett större aktivt engagemang under kursen samt att se om potential finns att effektivisera undervisningen m.a.p. lärarinsatsen, genom att lyfta över en del av enklare rutinkontroller till de studerande själva.

    Kamratbedömning har implementerats i två sinsemellan likartade kurser inom beräkningsmekanik vid högskole- resp. civilingenjörsprogrammen i Maskinteknik, LiTH (600 studenter ingick i studien). Mer specifikt har till två enklare inledande laborationsuppgifter inkluderats ett moment av kamratbedömning. Utvärderingen av det genomförda arbetet har skett via en kvalitativ studie, där de studerandes perspektiv/synpunkter inhämtats i samband med skriftlig redovisning av inlämningsuppgifter. Utöver detta har den kursansvarige gjort observationer av hur kamratutvärderingsarbetet fortskridit under laborationstid.

    Resultatet visar att de studerande har uppskattat granskningen av såväl det egna som kamraternas arbeten, och att de sett det som ett led i lärandeprocessen. Även professionsperspektivet har lyfts fram där de studerande betonar vikten av moment och uppgifter i utbildningen som har en direkt relevans i det kommande yrkeslivet. Den kursansvariges bedömning är vidare att andelen ”viktiga” och ”relevanta” frågor ökat, vilket ger indikationer på att kamratbedömning kan vara en såväl pedagogiskt som effektivitetsmässigt gynnsam metodik. De studerande har dock upplevt logistiken/administrationen kring kamratvärderingen som i vissa avseenden besvärlig.

    Sammanfattningsvis är det vår slutsats att kamratbedömning har en stor potential att berika utbildningar m.a.p. förmåga till kritisk granskning, djupinlärning och effektivisering, men att verksamheten inte bara skall implementeras kursvis (med risk för suboptimering och ineffektivitet), utan att den bör inlemmas i ett större perspektiv, med progression genom utbildningen som riktmärke.

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  • 286.
    Sjöberg, Birgitta Janero
    et al.
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Subaortic flow profiles in aortic valve disease: a two-dimensional color Doppler study.1994In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 7, no 3 Pt 1, p. 276-285Article in journal (Refereed)
    Abstract [en]

    With time-corrected color Doppler echocardiography, the aortic subvalvular spatial flow velocity profile was registered in two perpendicular planes in 10 patients with aortic valve disease and in 5 healthy control subjects. Patients with predominant aortic valve stenosis had a fairly flat profile, and the subvalvular diameter, obtained from left parasternal two-dimensional tissue imaging, provided a good estimate of the mean of the two transverse flow axes. This explains the accuracy in determination of stroke volume and aortic valve area that is reported in studies on patients with aortic valve stenosis when the continuity equation is used. However, the use of apical pulsed Doppler ultrasound registrations from the left ventricular outflow tract and parasternal two-dimensional echocardiography for flow area calculation may introduce large errors in calculated stroke volume in certain patients with aortic regurgitation and in normal subjects, because of a non-flat spatial velocity profile or an inaccurate estimate of flow area.

  • 287.
    Sjöberg, Birgitta Janero
    et al.
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Eidenvall, L
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Vascular characteristics influence the aortic ultrasound Doppler signal: computer and hydraulic model simulations.1993In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 147, no 3, p. 271-279Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for non-invasive methods for the assessment of left ventricular function. Ultrasound Doppler methods are promising, and the early systolic flow velocity signal immediately distal to the aortic valve has been used clinically for this purpose. However, the signal is influenced not only by left ventricular ejection but also by systemic vascular characteristics. Their relative contribution to the time-velocity signal has not been analysed in depth previously. A theoretical analysis, based on a three-element Windkessel model, neglecting peripheral outflow in early systole and assuming linear pressure rise, was therefore tested in computer and hydraulic model simulations where peripheral outflow was included. Significant changes in early aortic flow velocity parameters were found when vascular characteristics were altered. As predicted by the theory, with a standardized aortic valve area and aortic pressure change, the simulations confirmed that maximal flow velocity is related to compliance of the aorta and the large arteries, and that maximal acceleration is inversely related to the characteristic impedance of the aorta. Therefore, maximal velocity and acceleration can be used for assessment of left ventricular function only in situations where vascular characteristics can be considered relatively constant or where they can be estimated.

  • 288.
    Sjögren, Jane
    et al.
    Lund University Hospital.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Arheden, Håkan
    Lund University Hospital.
    Heiberg, Einar
    Lund University Hospital.
    Prototype Based Image Segmentation - A Novel Method to Incorporate a Priori Information in a Level Set Method2008In: SSBA Symposium Lund 13-14 mars 2008,2008, 2008Conference paper (Refereed)
  • 289.
    Sjölinder, Emil
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Spray and Wall Film Modeling with Conjugate Heat Transfer in OpenFOAM2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis was provided by Scania AB. The objective of this thesis was to modify an application in the free Computational Fluid Dynamics software OpenFOAM to be able to handle spray and wall film modeling of a Urea Water Solution together with Conjugate Heat Transfer. The basic purpose is to widen the knowledge of the vaporization process of a Urea Water Solution in the exhaust gas after treatment system for a diesel engine by using OpenFOAM. First, urea has been modeled as a very viscous liquid at low temperature to mimic the solidication process of urea. Second, the development of the new application has been done. At last, test simulations of a simple test case are performed with the new application. The results are then compared with simplied hand calculations to verify a correct behavior of certain exposed source terms. The new application is working properly for the test case but to ensure the reliability, the results need to be compared with another Computational Fluid Dynamics software or more preferable, real experiments. For more advanced geometries, the continued development presented last in this thesis is highly recommended to follow.

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    spray_wall_film_cht_openfoam
  • 290.
    Skoog, Pontus
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Fluidrörelse- och värmetransportsmodellering i götugn2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [sv]

    The purpose of this thesis for Sapa Heat Transfer is to examine a furnace in which aluminium is pre-heated before hot rolling. The project is modeled in a computer environment in which the air flow in the furnace and the heat transfer to the aluminium solids are included. The computer environment and its governing equations, as well as boundary conditions and generalizations, are presented and explained.

    The simulations are based on two models. The first model has an asymmetric solid placement, which is how it looks in today's ovens. It is validated against collected data. The second model has a symmetric solid placement, in which improvements are introduced and evaluated.

    The results indicate that a symmetric positioning of metal solids in the oven is preferable in order to achieve a good airflow distribution. The use of plates has been proven useful for steering the air to critial areas and to get an even distribution of the airflow. Lastly the simulations indicate that an increased airflow can compensate the less optimal flow distribution that arises with asymmetric solid placements.

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  • 291.
    Spjutare, Christian
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics .
    Aerodynamic Loads on External Stores - Saab 39 Gripen: Evaluation of CFD methods for estimating loads on external stores2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    External stores mounted on aircraft generate loads which need to be estimated before first takeoff. These loads can be measured in a wind tunnel but since the possible store configurations are basically endless, testing them all is neither economically feasible nor time efficient. Thus, scaling based on geometrical similarity is used. This can, however, be a crude method. Stores with similar geometrical properties can still behave in different ways due to aerodynamic interference caused by adjacent surfaces.

    To improve the scaling performance, this work focuses on investigating two CFD codes, ADAPDT and Edge. The CFD simulations are used to derive the difference in aerodynamic coefficients, or the Δ-effect, between a reference store and the new untested store. The Δ-effect is then applied to an existing wind tunnel measurement of the reference store, yielding an estimation of the aerodynamic properties for the new store.

    The results show that ADAPDT, using a coarse geometry representation, has large difficulties predicting the new store properties, even for a very simple store configuration on the aircraft. Therefore it is not suited to use as a scaling tool in its present condition. Edge on the other hand uses a more precise geometry representation and proves to deliver good estimations of the new store load behavior. Results are well balanced and mainly conservative. Some further work is needed to verify the performance but Edge is the recommended tool for scaling.

     

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  • 292. Sun, Y
    et al.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Sjöberg, Birgitta Janero
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Eidenvall, L
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images.1995In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 8, no 6, p. 904-914Article in journal (Refereed)
    Abstract [en]

    A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (+/- 10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

  • 293. Sun, Y
    et al.
    Sjöberg, Birgitta Janero
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Mathematical model that characterizes transmitral and pulmonary venous flow velocity patterns.1995In: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 268, no 1 Pt 2, p. H476-89Article in journal (Refereed)
    Abstract [en]

    The transmitral and pulmonary venous flow velocity (TMFV and PVFV, respectively) patterns are related to the physiological state of the left heart by use of an electrical analog model. Filling of left ventricle (LV) through the mitral valve is characterized by a quadratic Bernoulli's resistance in series with an inertance. Filling of the left atrium (LA) through the pulmonary veins is represented by a lumped network of linear resistance, capacitance, and inertance. LV and LA are each represented by a time-varying elastance. A volume dependency is incorporated into the LV model to produce physiological pressure-volume loops and Starling curves. The state-space representation of the analog model consists of 10 simultaneous differential equations, which are solved by numerical integration. Model validity is supported by the following. First, the expected effects of aging and decreasing LV compliance on TMFV and PVFV are accurately represented by the model. Second, the model-generated TMFV and PVFV waveforms fit well to pulsed-Doppler recordings in normal and postinfarct patients. It is shown that the TMFV deceleration time is prolonged by the increase in LV compliance and, to a lesser extent, by the increase in LA compliance. A shift from diastolic dominance to systolic dominance in PVFV occurs when LA compliance or pulmonary perfusion pressure increases or when LV compliance or mitral valve area decreases. The present model should serve as a useful theoretical basis for echocardiographic evaluation of LV and LA functions.

  • 294. Sun, Ying
    et al.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Sjöberg, Birgitta Janero
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Eindvall, Lars
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images1997In: Journal of the American College of Cardiology, ISSN 0735-1097, E-ISSN 1558-3597, Vol. 8, no 6, p. 904-914Article in journal (Refereed)
    Abstract [en]

    A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (±10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

  • 295.
    Sund-Levander, Märtha
    et al.
    Linköping University, Department of Medicine and Health Sciences, Clinical Physiology . Linköping University, Faculty of Health Sciences.
    Grodzinsky, Ewa
    Linköping University, Department of Medicine and Health Sciences, Primary Care . Linköping University, Faculty of Health Sciences.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Wahren, Lis Karin
    Linköping University, Department of Social and Welfare Studies. Linköping University, Faculty of Health Sciences.
    Errors in body temperature assessment related to individual variation, measuring technique and equipment2005In: International journal of nursing practice, ISSN 1322-7114, Vol. 10, no 5, p. 216-223Article in journal (Refereed)
    Abstract [en]

    Errors in body temperature measurement might seriously influence the evaluation of an individual's health condition. We studied individual variation, measurement technique and the equipment used when assessing body temperature. In the first part of the study, three volunteers performed repeated measurements for five mornings. In the second part, the morning rectal, oral, ear and axillary temperatures were measured once in 84 men and women (19–59 years). The repeated measurements showed a daily temperature difference of 0.1–0.4°C in rectal and oral temperatures, 0.2°C−1.7°C in the ear and 0.1–0.9°C in the axillary temperatures. In the sample of 84 subjects, men and postmenopausal women had a lower mean body temperature compared to premenopausal women. The mean deviation between rectal temperature, and oral, ear and axillary temperatures, respectively, was > 0.5°C, with a large individual variation. In conclusion, in order to improve the evaluation of body temperature, the assessment should be based on the individual variation, the same site of measurement and no adjustment of oral, ear or axillary temperatures to the rectal site.

  • 296.
    Szabó, Zoltan
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Sjökvist, Stefan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Gustavsson, Torbjörn
    Carleberg, Per
    Uppsäll, Magnus
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Berg, Sören
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Ahn, Henrik
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Intraoperativ visualisering av myokardiell perfusion i realtidmeaugmented reality temperatur monitorering-en experimentellstudie2013Conference paper (Other academic)
  • 297.
    Szabó, Zoltán
    et al.
    Linköping University, Department of Medical and Health Sciences, Cardiothoracic Anaesthesia and Intensive care. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Berg, Sören
    Linköping University, Department of Medical and Health Sciences, Cardiothoracic Anaesthesia and Intensive care. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Sjökvist, Stefan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Thermirage AB, Linköping, Sweden.
    Gustafsson, Torbjörn
    Thermirage AB, Linköping.
    Carleberg, Per
    Thermirage AB, Linköping.
    Uppsäll, Magnus
    Thermirage AB, Linköping.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ahn, Henrik
    Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Real-time intraoperative visualization of myocardial circulation using augmented reality terperature display2013In: The International Journal of Cardiovascular Imaging, ISSN 1569-5794, E-ISSN 1875-8312, Vol. 29, no 2, p. 521-528Article in journal (Refereed)
    Abstract [en]

    For direct visualization of myocardial ischemia during cardiac surgery, we tested the feasibility of presenting infrared (IR) tissue temperature maps in situ during surgery. A new augmented reality (AR) system, consisting of an IR camera and an integrated projector having identical optical axes, was used, with a high resolution IR camera as control. The hearts of five pigs were exposed and an elastic band placed around the middle of the left anterior descending coronary artery to induce ischemia. A proximally placed ultrasound Doppler probe confirmed reduction of flow. Two periods of complete ischemia and reperfusion were studied in each heart. There was a significant decrease in IR-measured temperature distal to the occlusion, with subsequent return to baseline temperatures after reperfusion (baseline 36.9 ± 0.60 (mean ± SD) versus ischemia 34.1 ± 1.66 versus reperfusion 37.4 ± 0.48; p < 0.001), with no differences occurring in the non-occluded area. The AR presentation was clear and dynamic without delay, visualizing the temperature changes produced by manipulation of the coronary blood flow, and showed concentrically arranged penumbra zones during ischemia. Surface myocardial temperature changes could be assessed quantitatively and visualized in situ during ischemia and subsequent reperfusion. This method shows potential as a rapid and simple way of following myocardial perfusion during cardiac surgery. The dynamics in the penumbra zone could potentially be used for visualizing the effect of therapy on intraoperative ischemia during cardiac surgery.

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  • 298.
    Szabó, Zoltán
    et al.
    Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Sjökvist, Stefan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Gustafsson, Torbjörn
    Thermirage AB, Linköping, Sweden.
    Uppsäll, Magnus
    Thermirage AB, Linköping, Sweden.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Berg, Sören
    Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Ahn, Henrik
    Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Real-time intraoperative visualization of myocardial circulation by augmented reality temperature display2010In: Minimally invasive therapy and allied technologies, Informa Healthcare, 2010, p. 61-61Conference paper (Other academic)
    Abstract [en]

    Background:  Intraoperative  ischemia   during   coronary   surgery   may   have   severe   consequences   for the patient and may also pose a difficult diagnostic problem  to the  surgeon.  There  is no  clinically used direct  method  to evaluate  the  effect on  the  circulation of various therapeutic maneuvers  to the heart. Augmented (mixed)  reality using projection  of color- coded  infra-red  (IR)  images onto  the imaged  tissues in real  time  may  give an  intuitive  representation of the tissue surface temperature and thus,  information about   myocardial   perfusion   on  the  surface  of  the organ itself.

    Purpose:  To demonstrate in animal experiments the feasibility of presenting  IR tissue temperature images  reflecting  myocardial  perfusion into  the  surgical  field  with  augmented reality.

    Method: We  have  constructed a  system  consisting of an IR camera  and  a projector  integrated in such a way that  they  have  identical  optical  axes,  solving the  geometrical  correspondence problem  in an easy way. In 5 pigs (weight = 57.5 ± 7 kg), the thorax was opened    by   median    sternotomy.   After   exposing the  heart,  an  elastic  vessel loop  was placed  around the  middle  of  the  left  descending  coronary  artery. A  2  mm   ultrasound  probe   was  inserted   distally around the LAD for flow velocity measurements. Subsequent ischemia-reperfusion periods  were induced using a fixed protocol. 

    Results:  The  time course of  an   occlusion   was  clearly  seen   in  quantitative curves  as well as in  color-coded temperature  maps on the surface of the heart.  The  difference in surface temperature between the three areas more or less affected  by  the  ischemia   was  also  clearly  demon- strated.  During  ischemia,  the surface of the myocardium  showed  concentrically  arranged  zones  of different temperatures (IR penumbra) potentially cor- responding to different  degrees  of severity of ischemia. 

    Conclusion: Surface  temperature changes  due to ischemia can be assessed quantitatively and visualized  in situ during occlusion of a coronary  artery and   subsequent  reperfusion of  the myocardium. This method shows potential  as  a  fast  and  simple way of  following  myocardial  perfusion  during surgery. The  change  of the  extension  of the  penumbra zone  is a potential monitoring device  for the  thera- pies used  in the salvage or prevention of ischemia  in experimental or clinical cardiac surgery and may introduce new practices in monitoring  duringcardiac  and vascular anesthesia.

  • 299.
    Söderström, Andreas
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A PML Based Non-Reflective Boundary for Free Surface Fluid Animation2010In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 29, no 5, p. 136-Article in journal (Refereed)
    Abstract [en]

    This article presents a novel non-reflective boundary condition for the free surface incompressible Euler and Navier-Stokes equations. Boundaries of this type are very useful when, for example, simulating water flow around a ship moving over a wide ocean. Normally waves generated by the ship will reflect off of the boundaries of the simulation domain and as these reflected waves returns towards the ship they will cause undesired interference patterns.By employing a Perfectly Matched Layer (PML) approach we have derived a boundary condition that absorbs incoming waves and thus efficiently prevents these undesired wave reflections. To solve the resulting boundary equations we present a fast and stable algorithm based on the Stable Fluids approach. Through numerical experiments we then show that our boundaries are significantly more effective than simpler reflection preventing techniques. We also provide a thorough analysis of the parameters involved in our boundary formulation and show how they effect wave absorption efficiency.

  • 300.
    Thelin, Fredrik
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    A CFD Analysis of Cyclodial Propellers2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The quest for more efficient machines is always ongoing in the engineering world. This project is no different. ABB are investigating a new type of propeller that seems to offer increased efficiency compared to normal screw propellers. That is a so called foil wheel propeller. The foil move in a circular pattern with the fluid stream moving in the radial direction of the propeller instead of the axial as in a screw propeller. If the propeller is placed and modeled correctly it can also be used as a thrust vectoring device. This report focuses on the fluid physics of the foil wheel propeller, or as it is called in this report radial flow propeller. First of all the movements and interactions of the blades must be understood. Both to keep the efficiency high to compete with screw propellers, but also to foresee any problems that may occur with such a new device. A scaled down version of the propeller have been commissioned by ABB and will be tested in some time after the work within this report is completed. The effects associated to this will also be analyzed. The tool to compute the flow physics of the radial flow propeller will be computational fluid dynamics. Computational fluid dynamics uses a numerical method to compute the entire fluid field in space and time. The flow around the propeller is highly complex so a detailed analysis is needed if a well functioning control system is to be constructed for instance. The differences between the downscale and the full-scale are great, even when the non dimensional coefficients are considered. The down-scale case will be less efficient, it will be difficulties predicting the performance of the full-scale since the downscale flow is much less powerful than the full-scale case. The interaction between the blades has a large effect. There is a strong relation between angle of attack and the number of blades. The forces that are large change by about 30\% so it must definitely be considered if a model is to be used for a control system.

    Download full text (pdf)
    FredrikThelin_Thesis2017.pdf
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