| Summary: | 碩士 === 國防大學中正理工學院 === 兵器系統工程研究所 === 92 === The implantation of vascular stents has become more popular to treat occlusive vascular disease like stenosis. Some disturbed blood flow patterns or changes of wall shear stress distributions happened because of the implantation of the vascular stents. The close correlation between the flow phenomenon in the vicinity of the stent and the localization of restenosis or thrombosis of which the mechanism is not well known has led researchers to investigate the geometric design of vascular stents which is associated with the non-uniform features of hemodynamics such as recirculation, stagnation etc.
In this study the detailed hemodynamic phenomena near the stent struts in the stented vessel was simulated by using the computational fluid dynamics (CFD). Steady flows with high and low Reynolds no. were applied to analysis the flow field between the wires of vascular stents for five different wire spacing design ( l/d = 3, 6, 9, 12, 15 ). Then the unsteady flows for the physiological situations of coronary and carotid artery with two different pulsatile volume flow wave forms were used to study the variation of pulsatile wall shear stress happened on the surface of those five different designs of stent struts.
Comparing with reference of the Newtonian case the consequences of the presence of a stent on the flow of blood inherent with the non-Newtonian properties can provide insight into how the non-Newtonian properties affect the flow patterns within the stent and the importance of the non-Newtonian properties. Velocity and its gradient of the flow field nearby the stent are decreased by the introduction of the non-Newtonian properties. At some specific time, the plug flow induced by the non-Newtonian properties will affect the hemodynamic features in the region close to the stent and increase the wall shear rate on the top of the stent comparing the numerical result of Newtonian fluid. The maximum value of wall shear stress created on the surface of the stent should be limited to avoid the breaking of red cell membrane and result in the improvement of the design of intravascular stents.
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