动脉局部狭窄时脉动流的有限元分析

本文利用有限元方法研究动脉局部狭窄下的脉动流流场,重点考查在50％与80％面积狭窄下的速度分布、压力分布、壁面剪应力分布及流动分离情况。几何形状及边界条件均模拟相应的脉动流实验模型。采用测得的随时间变化的速度分布作为入口端条件,并利用罚函数和逆风格式等计算技巧得出了光滑的与实验基本相符的速度、压力波形。本文讨论了不同狭窄下速度、压力、壁面剪应力的分布形态,给出了脉动流中狭窄处局部流动分离的间歇性变化规律,并结合实验与临床应用进行了讨论。

THE FINITE ELEMENT ANALYSIS OF PULSATILE FLOW PATTERNS ASSOCIATED WITH AN ARTERIAL STENOSIS

Pulsatile flow patterns in rigid arterial models with stenosis (area constrictions) of 50% and 80% have been studied using the Finite Element Methods. Flow patterns of the constricted region have been investigated for a simulated physiological condition with an average Reynolds number of 561.8 and a Womersley number of 7.16. Velocity waveforms, axial pressure drop and wall shear stress distributions have been computed for each model and presented at several time steps. Flow separation zone near the stenosis was also studied. Results have been validated by comparing the recordings of Doppler velocimeter obtained in the in vitro experiments by the authers, and by other experimental work reported in the literature.Results showed thai due to the stenosis,1) the peak values of velocity, pressure drop arid wall shear stress increase; 2) waveforms of these three variables broaden and phase differences appear; 3) flow separations occur. It is noted that among the three variables, the wall shear stress is the most sensible indicator to the degree of stenosis. Results also showed that 4)-pulsatile flow separation occurs at both sides of the stenosis in an"off and on" manner; and 5) the maximum wall shear stress of flow in 80% stenotic model is very close to the value of 40 Pa qucted to cause a cute endothelial disruption (Fry, 1968).