Research on the Interaction of the Turbulent Free Shear Layer with Walls.

本课题利用两台激光多普勒测速仪，对自由剪切层与相邻壁面再附着过程中湍流速度波动的两点空间相关性进行了研究。由于正在进行的实验室建筑维修工作，最初的时间表被改变了几次。结果总结；提出了用两台激光多普勒测速仪同时测量两点空间相关的方法。(1)研究了两个LDV系统时钟频率微小差异的影响，并采用多重采样技术减小了这种不完全同步带来的误差。(2)利用DMA传输和机器语言编写的滤波程序，实现了对采样数据的实时处理。(3)完成了用两台计算机和两台激光多普勒测速仪同时进行数据采集的系统。测量了平板前缘形成的长气泡湍流剪切层内速度波动的两点空间相关性。定量地得到了在长泡前缘区域观测到的低频波动传播的影响。

This research project was made to get the two-point space correlation of turbulent velocity fluctuations within the reattaching process of the free shear layers to the adjacent walls by using two Laser-Doppler Velocimeters. The initial schedule was changed several times because of the ongoing repair work of the laboratory building. Summarizing the results;1. The measuring method of the two-point space correlation using two Laser Doppler Velocimeters simultaneously is presented. (1) The effect of minor disagreement of the clock frequencies of two LDV systems is studied and the error introduced by this incomplete synchronization has been reduced by using multiple sampling technique. (2) The real time processing of the sampled data has been realized through use of the DMA transfer and machine language written filtering programs. (3) The data sampling system using two computers with two Laser Doppler Velocimeters simultaneously is completed.2. Two-point space correlation of the velocity fluctuations within the turbulent shear layer of the long bubble formed on the leading edge of a flat plate is measured. The influence of the propagation of low frequency fluctuations observed within the leading edge region of the long bubble is quantitatively obtained.