Quantifying turbulent wall shear stress in a subject specific human aorta using large eddy simulation

• Published in: Medical engineering & physics Vol. 34; no. 8; pp. 1139 - 1148
• Main Authors: Lantz, Jonas, Gårdhagen, Roland, Karlsson, Matts
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2012; Elsevier
• Subjects: Aorta; Aorta - physiology; Aortic arch; Atherosclerosis; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Blood Circulation; Boundaries; Cardiology. Vascular system; Computational fluid dynamics; Computer Simulation; Decomposition; Heart; Heart - physiology; Hemorheology; Human aorta; Humans; Hydrodynamics; Magnetic Resonance Imaging; Male; Mechanical stimuli; Medical sciences; Radiology; Reynolds decomposition; Scale resolving turbulence model; Spatio-Temporal Analysis; Stress, Mechanical; TECHNOLOGY; TEKNIKVETENSKAP; Wall shear stress; Wall shear stress; Scale resolving turbulence model; Reynolds decomposition; Computational fluid dynamics; Human aorta; Atherosclerosis; Human; Turbulence; Cardiovascular disease; Artery; Vascular disease; Large eddy simulation; Mechanical stress; Blood vessel; Shear stress; Aorta; Models; Circulatory system; Biomedical engineering
• DOI: 10.1016/j.medengphy.2011.12.002
• ISSN: 1350-4533; 1873-4030

In this study, large-eddy simulation (LES) is employed to calculate the disturbed flow field and the wall shear stress (WSS) in a subject specific human aorta. Velocity and geometry measurements using magnetic resonance imaging (MRI) are taken as input to the model to provide accurate boundary conditions and to assure the physiological relevance. In total, 50 consecutive cardiac cycles were simulated from which a phase average was computed to get a statistically reliable result. A decomposition similar to Reynolds decomposition is introduced, where the WSS signal is divided into a pulsating part (due to the mass flow rate) and a fluctuating part (originating from the disturbed flow). Oscillatory shear index (OSI) is plotted against time-averaged WSS in a novel way, and locations on the aortic wall where elevated values existed could easily be found. In general, high and oscillating WSS values were found in the vicinity of the branches in the aortic arch, while low and oscillating WSS were present in the inner curvature of the descending aorta. The decomposition of WSS into a pulsating and a fluctuating part increases the understanding of how WSS affects the aortic wall, which enables both qualitative and quantitative comparisons.