| dc.description.abstract | Heart disease is the leading cause of death globally. Aorta is extremely important because of its critical function in blood circulation. Abnormal hemodynamics of aortic valve and arch is related to many severe diseases and has intrigued a growing of fluid dynamic researches over decades. However, due to the complexity of transient flow and fluid-structure interaction, many aspects of aortic hemodynamics have not been fully understood. The goal of this dissertation is to design and construct an in-vitro cardiovascular flow simulator for PIV hemodynamics research and understand the pulsatile flow characteristics of human aortic valve and arch under normal and diseased conditions. First, we investigated the fluid dynamics of a complaint aortic root model under varied cardiac outputs. High turbulence kinetic energy was observed after peak systole. A reduction in cardiac outputs resulted in a lower post-systole turbulence, smaller circumferential deformation, smaller geometric orifice area, and a shortened valve-opening period.
Second, we investigated the pulsatile flow through stenotic aortic valve models. Results indicated that a severe prosthetic stenosis causes significant changes in the flow fields downstream. The hemodynamic changes, e.g., increased jet velocity and viscous shear stress, were associated with the stiffened leaflet materials, rather than the stent base structure.
Third, we presented a combined experimental and numerical study of the pulsatile flow characteristics within Gothic and Romanesque aortic arch models. The results revealed significantly different primary and secondary flow characteristics between two models. Low and oscillatory wall shear stress and the abnormal secondary flow in the Gothic arch are correlated to vascular endothelial cell remodeling and might provide hints to the increased risks of atherosclerosis, late systemic hypertension, and other cardiovascular complications.
Overall, this dissertation provides physical insights into pulsatile flow characteristics through aortic valve and arch models under varied normal and diseased conditions. In-vitro experiments using PIV can capture prominent flow characteristics within prosthetic aortic models, providing better controllability and spatial resolution that complements clinical diagnosis and a source of validation for computational simulations. Future improvements of artificial models’ designs and the advanced flow diagnostic techniques can further enhance the accuracy and credibility of in-vitro flow researches. | en_US |
