Schwarz A C, Tiederman W G, Phillips W M
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907.
J Biomech Eng. 1988 May;110(2):123-8. doi: 10.1115/1.3108416.
Elevated turbulent shear stresses associated with sufficient exposure times are potentially damaging to blood constituents. Since these conditions can be induced by mechanical heart valves, the objectives of this study were to locate the maximum turbulent shear stress in both space and time and to determine how the maximum turbulent shear stress depends on the cardiac flow rate in a pulsatile flow downstream of a tilting disk valve. Two-component, simultaneous, correlated laser velocimeter measurements were recorded at four different axial locations and three different flow rates in a straight tube model of the aorta. All velocity data were ensemble averaged within a 15 ms time window located at approximately peak systolic flow over more than 300 cycles. Shear stresses as high as 992 dynes/cm2 were found 0.92 tube diameters downstream of the monostrut, disk valve. The maximum turbulent shear stress was found to scale with flow rate to the 0.72 power. A repeatable starting vortex was shed from the disk at the beginning of each cycle.
与足够暴露时间相关的升高的湍流剪切应力可能会对血液成分造成损害。由于这些情况可能由机械心脏瓣膜引发，本研究的目的是在空间和时间上确定最大湍流剪切应力，并确定最大湍流剪切应力如何取决于倾斜盘式瓣膜下游脉动流中的心脏流速。在主动脉直管模型中，在四个不同的轴向位置和三个不同的流速下记录了双分量、同步、相关激光测速仪测量数据。所有速度数据在位于大约收缩期峰值流的15毫秒时间窗口内进行了300多个周期的总体平均。在单支柱盘式瓣膜下游0.92个管径处发现剪切应力高达992达因/平方厘米。发现最大湍流剪切应力与流速的0.72次方成比例。在每个周期开始时，从盘上脱落一个可重复的起始涡旋。
