Real-time Diagnosis of Flow by Using Pressure Wave

本研究的目的是开发一种基于计算机数值计算的流动诊断方法。流动诊断是指对管道或流体机械流场中的障碍物或空洞进行检测和识别。首先，在一般流道处理之前，先进行简单形状的充满水的封闭水池的基础研究。在由丙烯酸树脂和黄铜制成的两种矩形储罐中产生高能量的小放电，并由于泄压突然产生气泡而产生脉冲压力波。实现了气泡的稳定产生、放电电路和传感电路的正确同步、极高频率信号的接收以及使用A/D转换器对计算机的高速数据访问，从而实现了高精度的流量测量。根据数据计算的结果表明，对于简单形状的障碍物(如球体)，一维方法给出了满意的解。虽然压力波阵面的实际形状是不稳定的、复杂的，但如果考虑波阵面穿过障碍体、折射到障碍体和绕过障碍体的情况，一维几何声学给出了高精度的解。然而，在计算墙体边界反射波时，一维解是不够的，应正确考虑墙体的声阻抗反射特性，而对于形状复杂的障碍体，则采用三维逆解。对波动方程必须进行计算。在本研究中，我们提出了一种三维边界元方法，给出了波动方程的高精度解。三维障碍物的轨道时间识别正在开发中，我们计划报告结果。

The puropose of the present research is to defvelop a flow diagnosis method on the basis of the numerical calculation on the computer. The flow diagnosis means detecting and identifying obstacles or cavities included in the flow field of pipes or fluid machines. At first, basic research wag performed for* a simple-shaped closed tank filled with water before general flow passage is treated. A small electric discharge with high energy was generated in two kinds of rectangular tanks, i. e., one made of acrylic resin and the etlier made of brass, and impulsive pressure wave was generated by sudden generation of a bubble due to the discliarge. Stable generation of the bubble, correct synchronization of a discharge circuit and a sensing circuit, receiving of signal having very high frequency, and high speed data access to the computer using A/D converter were achieved and highly accurate measurement of flow was possible. According to the results calculated from the data, it was shown that a one-dimensional method gives a satisfactory solution for an obstacle of simple shape (e. g., sphere). Although the actual shape of pressure wave front is unsteady and complex, the one-dimensional geometric - acoustics gives a solution with high accuracy if the wave fronts are considered of passing through, refracting on and diffracting around the obstacle body. However, in calculating the reflection wave from the wall boundar the one - dimensional solution was not adequate but, the reflection property due to acoustic impedance of the wall should be considered correctly., On the other hand, in the case of obstacle body of complex shape, three-dimensional inverse solution. to the wave equation must be calculated. In the present research, we proposed a three-dimensional boundary element method which gives high accuracy solution to the wave equation. The rail-time identification of three-dimensional obstacles is under development and we plan to report the results.