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

1.激光流动可视化系统我们开发了激光流动可视化系统，使我们能够观察到洁净室内湍流气流的微观结构。我们获得了许多洁净室内湍流可视化的静态照片，并将湍流可视化记录在录像带上。基于k-lt；epsilon&gt；湍流模型对洁净室内的空气流动进行了三维数值模拟。数值计算结果与流动显示结果吻合较好。然而，流动可视化使我们不仅可以很容易地了解整个流动结构，而且可以很容易地了解小尺度的微观湍流结构。2.激光多普勒测速仪我们研制了激光多普勒测速仪测量气流的系统。在洁净室里测量空气速度是相当困难的。气流速度很慢，多普勒信号的采样率很低，无法获得连续的速度波动。为此，我们设计了播种系统，以提高采样率，并取得了成功。最好的种子颗粒是铝金属颗粒(3-4)，其次是DOP雾化颗粒。比较了LDV风速仪和常规风速计的风速测量结果，其中串联式平行热线风速计是其中的一种。证明了激光测速仪在测量湍流特性方面具有很大的潜力。3.图像处理利用激光可视化系统，通过图像处理的方法，从视频图像中提取示踪剂浓度分布图。因此，我们能够定量地理解污染扩散的机制。

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.