用激光多卜勒风速仪研究畸变模拟器的三元速度场

作者用同点双测法 ,藉一台 5 5 X二维激光多卜勒风速仪 ( LDA)对多种畸变模拟器的图 1　同点双侧法试验布置图三元速度场进行了研究。试验布置见图 1。图 1 a为侧视图 ,1 b为上视图。当三束激光从侧面射入玻璃窗 ,可以测出轴向分速 Vx及切向分速 Vs。当激光束从进口沿轴向射入 ,则可测出径向分速Vr 及 Vs。畸变模拟器可绕轴转动 ,激光束交点藉位移机构可沿径向移动 ,再使用各种长度的直管 ,就可获得任意截面的三元速度场。前透镜焦距应选大些 ,以防影响模型的进口流场。图 2　速度矢量图二、典型结果与讨论　　图 2例示 90°扇形圆环畸…

APPLICATION LDA TO INVESTIGATION OF 3-D VELOCITY PATTERN IN INLET DISTORTION SIMULATOR

A two measurement at one point method with a two colour LDA(Laser Doppler Anemometer)has been used for measuring three dimensional velocity field.Various velocity distortions of the simulator have been investigated.The velocity and turbulence patterns of 90 degree torus quadrant and of torus with 20 degree slanted cut are shown.It can be seen clearly how the low velocity and large turbulence region will be caused by the flow separation from the duct lips.In order to estimate maximum instantaneous distortion,the vortex size must be measured.It is defined classically by velocity crelation and more directly than by total pressure.Some typical results are shown in a table.The vortex size is increased by the flow velocity.At 1D section the vortex size of torus with 20 degree slanted cut is about two times larger than the size of 90 degree torus quadrant.But at 3D section the former decreases and the later increases slightly.