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Andersson, M., Lantz, J., Ebbers, T. & Karlsson, M. (2015). Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation - Impact of Virtual Interventions. Cardiovascular Engineering and Technology, 6(6), 281-293
Open this publication in new window or tab >>Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation - Impact of Virtual Interventions
2015 (English)In: Cardiovascular Engineering and Technology, ISSN 1869-408X, E-ISSN 1869-4098, Vol. 6, no 6, p. 281-293Article in journal (Refereed) Published
Abstract [en]

Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
Computational fluid dynamics, Large eddy simulation, Turbulent kinetic energy, Flow displacement, Non-Newtonian, Virtual treatment, Magnetic resonance imaging
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-114496 (URN)10.1007/s13239-015-0218-x (DOI)000380356800007 ()
Note

Funding agencies: Swedish Research Council; Center for Industrial Information Technology (CENIIT); Swedish National Infrastructure for Computing (SNIC)

Available from: 2015-02-24 Created: 2015-02-24 Last updated: 2017-12-04Bibliographically approved
Karlsson, M., Andersson, M. & Lantz, J. (2014). Quantitative Assessment of Wall Shear Stress in an Aortic Coarctation - Impact of Virtual Interventions. In: Abstract: L7.00007 : Quantitative Assessment of Wall Shear Stress in an Aortic Coarctation - Impact of Virtual Interventions: . Paper presented at 67th Annual Meeting of the APS Division of Fluid Dynamics. Maryland, 59
Open this publication in new window or tab >>Quantitative Assessment of Wall Shear Stress in an Aortic Coarctation - Impact of Virtual Interventions
2014 (English)In: Abstract: L7.00007 : Quantitative Assessment of Wall Shear Stress in an Aortic Coarctation - Impact of Virtual Interventions, Maryland, 2014, Vol. 59Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Turbulent and wall impinging blood flow causes abnormal shear forces onto the lumen and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, wall shear stress (WSS) and related flow parameters were studied in a pre-treated aortic coarctation (CoA) as well as after several virtual interventions using computational fluid dynamics (CFD). Patient-specific geometry and flow conditions were derived from magnetic resonance imaging (MRI) data. Finite element analysis was performed to acquire six different dilated CoAs. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Pre-intervention, the presence of jet flow wall impingement caused an elevated WSS zone, with a distal region of low and oscillatory WSS. After intervention, cases with a more favorable centralized jet showed reduced high WSS values at the opposed wall. Despite significant turbulence reduction post-treatment, enhanced regions of low and oscillatory WSS were observed for all cases. This numerical method has demonstrated the morphological impact on WSS distribution in an CoA. With the predictability and validation capabilities of a combined CFD/MRI approach, a step towards patient-specific intervention planning is taken.  

Place, publisher, year, edition, pages
Maryland: , 2014
Keywords
Computation fluid dynamics, Large eddy simulation, Wall Shear Stress, Virtual treatment, Aortic Coarctation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-114489 (URN)
Conference
67th Annual Meeting of the APS Division of Fluid Dynamics
Available from: 2015-02-24 Created: 2015-02-24 Last updated: 2018-07-19
Andersson, M., Lantz, J. & Karlsson, M. (2014). Turbulence Quantification of Stenotic Blood Flow Using Image-Based CFD: Effect of Different Interventions. In: WCB 2014: . Paper presented at 7th World Congress of Biomechanics (WCB 2014), July 6-11, 2014, Boston, Massachusetts, USA.
Open this publication in new window or tab >>Turbulence Quantification of Stenotic Blood Flow Using Image-Based CFD: Effect of Different Interventions
2014 (English)In: WCB 2014, 2014Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Turbulent blood flow is often associated with some sort of cardiovascular disease, e.g. sharp bends and/or sudden constrictions/expansions of the vessel wall. The energy losses associated with the turbulent flow may increase the heart workload in order to maintain cardiac output (CO). In the present study, the amount of turbulent kinetic energy (TKE) developed in the vicinity of an aortic coarctation was estimated pre-intervention and in a variety of post-intervention configurations, using scale-resolved image-based computational fluid dynamics (CFD). TKE can be measured using magnet resonance imaging (MRI) and have also been validated with CFD simulations [1], i.e. a parameter that not only can be quantified using simulations but can also be measured by MRI.

Patient-specific geometry and inlet flow conditions were obtained using contrast-enhanced MR angiography and 2D cine phase-contrast MRI, respectively. The intervention procedure was mimicked using an inflation simulation, where six different geometries were obtained. A scale-resolving turbulence model, large eddy simulation (LES), was utilized to resolve the largest turbulent scales and also to capture the laminar-to-turbulent transition. All cases were simulated using baseline CO and with a 20% CO increase to simulate a possible flow adaption after intervention.

For this patient, results shows a non-linear decay of the total amount of TKE integrated over the cardiac phase as the stenotic cross-sectional area is increased by the intervention.  Figure 1 shows the original segmented geometry and two dilated coarctation with corresponding volume rendering of the TKE at peak systole. Due to turbulent transition at a kink upstream the stenosis further dilation of the coarctation tends to restrict the TKE to a plateau, and continued vessel expansion may therefore only induce unnecessary stresses onto the arterial wall. 

This patient-specific non-invasive framework has shown the geometrical impact on the TKE estimates. New insight in turbulence development indicates that the studied coarctation can only be improved to a certain extent, where focus should be on the upstream region, if further TKE reduction is motivated. The possibility of including MRI in a combined framework could have great potential for future intervention planning and follow-up studies.  

[1] J. Lantz, T. Ebbers, J. Engvall and M. Karlsson, Numerical and Experimental Assessment of Turbulent Kinetic Energy in an Aortic Coarctation, Journal of Biomechnics, 2013. 46(11): p. 1851-1858.

Keywords
Computational fluid dynamics, Large eddy simulation, Turbulent kinetic energy, Flow displacement, Non-Newtonian, Carreau, Virtual treatment, Magnetic resonance imaging
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:liu:diva-111042 (URN)
Conference
7th World Congress of Biomechanics (WCB 2014), July 6-11, 2014, Boston, Massachusetts, USA
Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2016-03-14
Andersson, M., Lantz, J. & Karlsson, M. (2013). NON-INVASIVE INTERVENTION PLANNING OF STENOTIC FLOWS USING SCALE-RESOLVED IMAGE-BASED COMPUTATIONAL FLUID DYNAMICS. In: : . Paper presented at Medicinteknikdagarna Stockholm, 2013. Linköping
Open this publication in new window or tab >>NON-INVASIVE INTERVENTION PLANNING OF STENOTIC FLOWS USING SCALE-RESOLVED IMAGE-BASED COMPUTATIONAL FLUID DYNAMICS
2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
Place, publisher, year, edition, pages
Linköping: , 2013
Keywords
Coarctation, Intervention, CFD, LES, Turbulence
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-98235 (URN)
Conference
Medicinteknikdagarna Stockholm, 2013
Available from: 2013-10-03 Created: 2013-10-03 Last updated: 2016-03-14Bibliographically approved
Pavlovic, S., Andersson, M., Lantz, J. & Karlsson, M. (2012). Reduced Aerodynamic Drag for Truck-Trailer Configurations Using Parametrized CFD Studies. In: ASME 2012 International Mechanical Engineering Congress and Exposition, Volume 7: Fluids and Heat Transfer Parts A, B, C, and D: . Paper presented at ASME 2012,International Mechanical Engineering Congress and Exposition, November 9-15, 2012, Houston, Texas, USA (pp. 1213-1220). New York, NY, USA: American Society of Mechanical Engineers
Open this publication in new window or tab >>Reduced Aerodynamic Drag for Truck-Trailer Configurations Using Parametrized CFD Studies
2012 (English)In: 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, Published 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.

Place, publisher, year, edition, pages
New York, NY, USA: American Society of Mechanical Engineers, 2012
Keywords
Drag reduction, aerodynamics, CFD, generic, scaled, bluff-body, rigid truck, trailer, device, flap, SST
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-98425 (URN)10.1115/IMECE2012-86816 (DOI)000350071100140 ()978-0-7918-4523-3 (ISBN)
Conference
ASME 2012,International Mechanical Engineering Congress and Exposition, November 9-15, 2012, Houston, Texas, USA
Available from: 2013-10-08 Created: 2013-10-08 Last updated: 2017-03-07Bibliographically approved
Andersson, M., Lantz, J. & Karlsson, M. (2011). Modeling of Subject Arterial Segments Using 3D Fluid Structure Interaction and 1D-0D Arterial Tree Network Boundary Condition. Paper presented at The 6th international symposium on biomechanics in vascular biology and cardiovascular disease.
Open this publication in new window or tab >>Modeling of Subject Arterial Segments Using 3D Fluid Structure Interaction and 1D-0D Arterial Tree Network Boundary Condition
2011 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Modeling of Subject Specific Arterial Segments Using 3D Fluid Structure Interaction and a 1D-0D Arterial Tree Network Boundary Condition

 

Magnus Andersson, Jonas Lantz , Matts Karlsson

 

Department of Management and Engineering, Linköping University, SE-581 83 Linköping, Sweden

 

Introduction

In recent years it has been possible to simulate 3D blood flow through CFD including the dilatation effect in elastic arteries using Fluid-Structure Interaction (FSI) to better match in vivo data. Patient specific imposed boundary condition (BC) is often used as the velocity profiles at the inlets. However, for the outlet BC a time-resolved pressure is required and often lacking as it is obtained by an invasive procedure. Numerous models have been developed for capturing the main effects of the vascular bed at these sites, which have been shown crucial and difficult to implement accurately. This work focus on a full scaled FSI simulation at an arterial section including the abdominal aorta, renal arteries and iliac bifurcations, obtained from MRI of an healthy individual. The outlet BC at the iliac arteries is connected with a 1D systemic arterial tree which is truncated with a 0D lumped model. This 3D-(0D-1D) connection can provide the essential features of the peripheral flow and, in contrast to the imposed BC, the 1D-0D coupling allow for investigation of cardiovascular diseases including stenoses and/or hypertension.

 

Methods

The MRI images were segmented using an in-house software to obtain a 3D surface of the vessel lumen, Figure 1. The surfaces were meshed with high quality hexahedral element using ANSYS ICEM CFD 12.0 (ANSYS Inc, Canonsburg, PA, USA). A PC-MRI time-resolved massflow at the descending aorta were used as inlet BC, where 22% of the flow was forced into the renal bifurcations assuming negligible pressure wave reflection. The wall was modelled with an isotropic elastic model with addition of an elastic support mimicking the damping effect of the surrounding tissue. The 1D model is based on transmission-line theory which involves an impedance model for the pressure-flow relationship. The arterial topology was extracted from literature and only the central arteries after the iliacs was considered. At the truncation sites a 3-element Windkessel model (known as RRC) was implemented and is the most common model of choice for describing the main effects of all the distal vessels.  The 1D system solves the Fourier frequency impedance coefficients over one heart cycle accounting for wave reflection by using the 15 first harmonics to obtain the corresponding pressure. The 3D-1D connection is done offline, which allows for an independent and more stable 3D simulation. This step is iteratively repeated until convergence is reach between the present 3D outlet flow and previous implemented 1D outlet flow. The simulation was utilized in ANSYS CFX, ANSYS Mechanical, and coupled by ANSYS Multi-Field.

 

Results

The (0D-1D)-3D model showed convergence of pressure/flow at the iliac outlets, Figure 2. The method provides realistic pressure and flow responses based on the input parameters and even capture the relative difference in flow/pressure distribution between the right and left illiac artery due to subject specific geometric variability. Parameters such as velocity profiles and WSS can be extracted in the 3D domain.

 

Conclusions

This method allows for a better insight of large scale vascular networks effect of the local 3D flow features and also gives a better representation of the peripheral flow compared to a pure 0D (lumped parameter/Windkessel) model. PC-MRI will provide data for validation of velocity profiles in the 3D model. Future work includes a subject specific 1D vascular topology to be combined with the 3D model.   

Keywords
Fluid Structure Interaction, Arterial Tree Network, 1D-0D Boundary Condition
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-77408 (URN)
Conference
The 6th international symposium on biomechanics in vascular biology and cardiovascular disease
Available from: 2012-06-13 Created: 2012-05-15 Last updated: 2016-03-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4656-7662

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