PULSATING FLOW IN CURVED PIPES SIMULATING AORTA

主动脉中的血液流动是一种复杂的周期性流动，其中包括高频成分。在这个主动脉弓上，循环系统故障是多发的。因此，即使在当今社会，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模拟主动脉的弯管进口区域内的振荡和脉动流动问题。通过流动显示方法和LDV测量，得到了以下速度分布结果。在振荡的水流上。弯管内的流动与上游切线处的流动密切相关，入口区域的流速分布随相变而变化很大。脉动流的入口长度小于定常流的入口长度，并且随着沃姆斯利数α的增大而变短。在脉动的水流上。当欧米伽=15-35ﾟ时，弯道附近的速度分布随位相变化很快。当欧氏数α=10时，弯管入口区的流动现象非常复杂。当欧米伽*15ﾟ时，弯管的内半截面发生反流，且在所有α值都具有最小流量的阶段。当α=10时，轴向速度分布的下降出现在弯管第四轮之后。脉动流的进口长度小于与脉动流的最大流量相同的定常流的进口长度。

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.