Development of Measuring Method of Air Flow in Clean Foom Using LDV and Image Processing of Flow Visualization with LLS

1.我们开发了激光流动显示系统，使我们能够观察洁净室中湍流气流的微小结构。我们获得了多张洁净室紊流可视化的静态照片，并对紊流可视化进行了录像记录。基于k- <epsilon>湍流模型对洁净室气流进行了三维数值模拟。在一般流型中，数值计算结果与流动显示吻合较好。然而，流动可视化不仅使我们能够很容易地理解整个流动结构，而且使我们能够很容易地理解小尺度的微小湍流结构。激光多普勒测速仪研制了用激光多普勒测速仪测量空气流量的系统。在洁净室中测量风速是相当困难的。由于空气的速度很慢，多普勒信号的采样率很低，不能得到连续的速度波动。为此，我们设计了一种提高采样率的播种系统，并取得了成功。最好的种子颗粒是铝金属颗粒（3 ~ 4 μ > m），其次是DOP雾。本文比较了LDV和传统风速仪对风速的测量结果，其中采用串联式平行热线风速仪。证明了LDV在测量湍流特性方面具有很高的潜力。但目前还需要进一步发展。图像处理利用激光可视化系统对视频图像进行图像处理，绘制出示踪剂浓度分布图。这样我们就能够定量地理解污染扩散的机理。

1.Laser Flow Visualization SystemWe have developed the Laser Flow Visualization System which enable us to observe the minute structure of turbulent air flow in a clean room. We have obtain many pieces of still photograph of visualized turbulent flow in clean room, and have also recorded the turbulent flow visualization on videotape. We conducted the 3-D numerical simulation based on k- <epsilon> turbulence model concerning with the air flow in a clean room. Numerical results and flow visualization corresponds well in general flow pattern. However, the flow visualization enable us to comprehend easily not only the whole flow structure but also the the minute turbulent structure of small scale.2.Laser Doppler VelocitymeterWe developed the measuring system of air flow by LDV (Laser Doppler Velocitymeter). It is quite difficult to measure the air velocity in a clean room. Air velocity is so slow that sampling ratio of doppler signal is very low, and we could not obtain continuous velocity fluctuation. So, we have devised the seeding system to improve the sampling ratio and have succeeded. The best seed particle is aluminium metal particle (3-4 <mu> m) and second is the mist of DOP. The measurements of air velocity both with LDV and with conventional anemometer, in this case tandem type parallel hot wire anemometer being used, have been compared. And it proved that LDV has high potential of measuring turbulent flow property. But at present it needs more development.3.Image ProcessingDistribution maps of tracer concentration are made from video image with Laser Visualization System through the image processing method. So we have been able to comprehend the mechanism of contamination diffusion quantitatively.