Author: Zhang, Wensen
Title: CFD simulation and DMD analysis of pulsatile flow in pathological vessels
Degree: M.Sc.
Year: 2021
Subject: Blood flow
Hong Kong Polytechnic University -- Dissertations
Department: Department of Mechanical Engineering
Pages: 84 pages : color illustrations
Language: English
Abstract: Pathological geometry of blood vessels is induced by cardiovascular diseases (CVD). The flow in the human vein system is pulsating so the time-varying nature of blood transportation in arteries results in the loading of biological tissues. In order to reveal the relationship between flow phenomena with wall shear stress (WSS) in abdominal aortic aneurysms (AAA), three-dimensional computational fluid dynamics (CFD) simulations were conducted on respectively Newtonian and non-Newtonian pulsatile flows in geometrically simplified pathological vessels. The immersed boundary-lattice Boltzmann method (IB-LBM) was employed to obtain the unsteady flow fields, as well as temporal and spatial distributions of wall shear stress (WSS), with the Reynolds number and Womersley number being fixed at 500 and 12, respectively. Comparisons of the characteristic flow structures and corresponding WSS distributions were made between the pathological and healthy vessels. It was found that the distributions of instantaneous axial WSS are closely correlated with vortex shedding and propagation. The Newtonian fluid promotes the formation of secondary and tertiary vortices during diastole phase of the cardiac cycle, whereas vortices are diffused in the distal region in non-Newtonian fluid. Coherent flow structures were extracted using the dynamic mode decomposition (DMD) method, which revealed that the low-frequency DMD modes significantly contributes to vortex formation and evolution while the higher frequency modes dominate rise and drop of WSS in proximal and distal wall of the dilation. The current research provides more physical insights into the connection between pulsatile Newtonian or non-Newtonian fluid flow and the associated WSS in pathological vessels.
Rights: All rights reserved
Access: restricted access

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