PULSATING FLOW IN CURVED PIPES SIMULATING AORTA

主动脉的血流是一种复杂的周期性血流，包含高频成分。这种主动脉弓常发生循环故障。因此，即使在我们今天的社会中，处理流体动力学也是非常重要的。为了揭示主动脉内流动发展的本质，有必要对弯曲管内的流动进行分析。本课题的目的是解决以主动脉为模型的弯曲管道入口区域的振荡和脉动流动问题。通过流动可视化方法和LDV测量，得到了以下速度分布结果：在振荡流上。弯曲管道内的流动与上游切线处的流动密切相关，入口区域的速度分布随相变化剧烈。振荡流的入口长度小于定常流，且随着沃默斯利数α的增大而变短。在脉动流上。当ω =15 ~ 35‰时，在弯曲弯道附近，速度分布随相位变化很快。弯管入口区发生的流动现象过于复杂，中间沃默斯利数α =10是不可能的。在所有α值下，流动反转发生在ω *15弯曲管的内半截面和最小流速相。当α =10时，轴向速度分布曲线在第四轮后出现下降。在流量相同的情况下，脉动流的入口长度小于稳定流的入口长度。

The blood flow in the aorta is a complex periodic flow that includes high frequency components. In this aortic arch circulatory faults occur frequently. Thus dealing with fluid dynamics has been of great importance even in our society today. In order to reveal the nature of flow development in the aorta, it is necessary to analyze the flow in curved pipes. The purpose of this project is to solve the problem of the oscillating and pulsating flows in the inlet region of curved pipes modelled on the aorta. By flow visualization method and LDV measurement, the following velocity distribution results were obtained.1. On the oscillating flow. The flow in the curved pipe is closely related to the flow in the upper stream tangent, and the velocity distribution changes drastically with the phase at the inlet region. The inlet length of the oscillating flow is less than that of the steady flow and becomes shorter as the Womersley number alpha increases.2. On the pulsating flow. The velocity distributions change rapidly with the phase at OMEGA=15-35ﾟ around the curved turn. The flow phenomena occurring in the entrance region of the curved pipes are too much complicated for an intermediate Womersley number alpha=10. The flow reversal occurs in the inner half cross-section of the curved pipe with OMEGA*15ﾟ and at phases with minimum flow rate for all values of alpha. And the depression in the axial velocity profile appears after the fouhth round in the curved pipe for alpha=10. The inlet length of pulsating flow is less than that of steady flow with the same flow rate as the maximum one in pulsating flow.