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Large eddy simulation of LDL surface concentration in a subject specific human aorta
Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-1942-7699
Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
2012 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 45, no 3, 537-542 p.Article in journal (Refereed) Published
Abstract [en]

The development of atherosclerosis is correlated to the accumulation of lipids in the arterial wall, which, in turn, may be caused by the build-up of low-density lipoproteins (LDL) on the arterial surface. The goal of this study was to model blood flow within a subject specific human aorta, and to study how the LDL surface concentration changed during a cardiac cycle. With measured velocity profiles as boundary conditions, a scale-resolving technique (large eddy simulation, LES) was used to compute the pulsatile blood flow that was in the transitional regime. The relationship between wall shear stress (WSS) and LDL surface concentration was investigated, and it was found that the accumulation of LDL correlated well with WSS. In general, regions of low WSS corresponded to regions of increased LDL concentration and vice versa. The instantaneous LDL values changed significantly during a cardiac cycle; during systole the surface concentration was low due to increased convective fluid transport, while in diastole there was an increased accumulation of LDL on the surface. Therefore, the near-wall velocity was investigated at four representative locations, and it was concluded that in regions with disturbed flow the LDL concentration had significant temporal changes, indicating that LDL accumulation is sensitive to not only the WSS but also near-wall flow.

Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 45, no 3, 537-542 p.
Keyword [en]
Low-density lipoprotein, Wall shear stress, Disturbed flow, Atherosclerosis
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:liu:diva-72895DOI: 10.1016/j.jbiomech.2011.11.039ISI: 000300863600019OAI: diva2:463535
funding agencies|Swedish Research Council| VR 2007-4085 VR 2010-4282 |National Supercomputer Centre (NSC)| SNIC022/09-11 |CMIV||Available from: 2011-12-09 Created: 2011-12-09 Last updated: 2013-09-12
In thesis
1. On Aortic Blood Flow Simulations: Scale-Resolved Image-Based CFD
Open this publication in new window or tab >>On Aortic Blood Flow Simulations: Scale-Resolved Image-Based CFD
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on modeling and simulation of the blood flow in the aorta, the largest artery in the human body. It is an accepted fact that abnormal biological and mechanical interactions between the blood flow and the vessel wall are involved in the genesis and progression of cardiovascular diseases. The transport of low-density lipoprotein into the wall has been linked to the initiation of atherosclerosis. The mechanical forces acting on the wall can impede the endothelial cell layer function, which normally acts as a barrier to harmful substances. The wall shear stress (WSS) affects endothelial cell function, and is a direct consequence of the flow field; steady laminar flows are generally considered atheroprotective, while the unsteady turbulent flow could contribute to atherogenesis. Quantification of regions with abnormal wall shear stress is therefore vital in order to understand the initiation and progression of atherosclerosis.However, flow forces such as WSS cannot today be measured with significant accuracy using present clinical measurement techniques. Instead, researches rely on image-based computational modeling and simulation. With the aid of advanced mathematical models it is possible to simulate the blood flow, vessel dynamics, and even biochemical reactions, enabling information and insights that are currently unavailable through other techniques. During the cardiac cycle, the normally laminar aortic blood flow can become unstable and undergo transition to turbulence, at least in pathological cases such as coarctation of the aorta where the vessel is locally narrowed. The coarctation results in the formation of a jet with a high velocity, which will create the transition to turbulent flow. The high velocity will also increase the forces on the vessel wall. Turbulence is generally very difficult to model, requiring advanced mathematical models in order to resolve the flow features. As the flow is highly dependent on geometry, patient-specific representations of the in vivo arterial walls are needed, in order to perform an accurate and reliable simulation. Scale-resolving flow simulations were used to compute the WSS on the aortic wall and resolve the turbulent scales in the complex flow field. In addition to WSS, the turbulent flow before and after surgical intervention in an aortic coarctation was assessed. Numerical results were compared to state-of-the-art magnetic resonance imaging measurements. The results agreed very well, suggesting that that the measurement technique is reliable and could be used as a complement to standard clinical procedures when evaluating the outcome of an intervention.The work described in the thesis deals with patient-specific flows, and is, when possible, validated with experimental measurements. The results provide new insights to turbulent aortic flows, and show that image-based computational modeling and simulation are now ready for clinical practice.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 66 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1493
National Category
Applied Mechanics
urn:nbn:se:liu:diva-85682 (URN)978-91-7519-720-3 (ISBN)
Public defence
2013-01-07, Nobel (BL32), B-huset, Campus Valla, Linköpings Universitet, Linköping, 09:00 (English)
Swedish Research CouncilSwedish Research Council
Available from: 2012-11-28 Created: 2012-11-28 Last updated: 2013-09-12Bibliographically approved

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