Document Type

Thesis - Open Access

Award Date

2017

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Stephen Gent

Abstract

The objective of this thesis is to computationally investigate the flow mechanics and the near-wall hemodynamics associated with the different take-off angles in the left coronary artery of the human heart. From this study, we will be able to evaluate if the increase in the take-off angles of the left coronary artery will significantly increases or decrease the likelihood of plaque (atherosclerosis) buildup in the left coronary artery bifurcations. This study quantifies the effects of the varying take-off angles on the branches along the left anterior descending (LAD) of the left coronary artery using computational fluid dynamics (CFD) simulations. The study aims to compare five test cases of the different take off-angles of the left coronary artery (LCA) and four different branch angles between the LAD and the left circumflex (LCx). It also considered the branch angles of the coronary artery downstream the LAD. The idealized geometries used for this study were constructed in SolidWorks 2015 and imported as surface meshes into Star-CCM+, a commercially available CFD solver. In this study, the LCA inlet boundary conditions was set as a pulsatile mass flow inlet and flow split ratios were set for the outlets boundary conditions that are representations of a middle age man at rest. The nature of blood pulsatile flow characteristic was accounted for and the properties of blood which include the density (1,050Kg/m3) and dynamic viscosity (0.0046Pa) were obtained from previous research. The results from the simulations are compared using established scales for the parameters evaluated. The parameters evaluated were: (i) Oscillatory Shear Index (OSI); which quantifies the extent in which the blood flow changes direction as it flows (ii) Time Average Wall Shear Stress (TAWSS); which quantifies the average shear stress experienced by the wall of the artery and (ii) Relative Residence Time (RRT); which defined how long blood spends in a location during blood flow. These parameters are used to predict the likelihood of blood clots, atherosclerosis, endothelial damage, plaque formation, and aneurysm in the blood vessels. The data from the simulations were analyzed using functional macros to quantify and generate threshold values for the parameters. Computational Fluid Dynamics has gain more recognition in field of medicine because it has been used to obtain the various mechanic behaviors of most artificial implanted devices used for endovascular and cardiovascular treatments before these devices are used in patients’ treatment. This can be a useful insight in coronary stenting, solid and stress analysis of biodegradable stent and can also provide insight into stenting for more complex arterial networks like brain stent grafts. In addition, it is important to understand the hemodynamics of the LCA before carrying out stent graft or angioplasty procedures. This will help determine the effectiveness of the stent graft in the coronary artery.

Library of Congress Subject Headings

Coronary arteries.
Computational fluid dynamics.
Hemodynamics.
Atherosclerosis -- Prevention.
Coronary heart disease -- Prevention.

Description

Includes bibliographical references (pages 97-106)

Format

application/pdf

Number of Pages

126

Publisher

South Dakota State University

Rights

Copyright © 2017 John Junior Asiruwa

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