A 3-D LASER DOPPLER VELOCIMETRY SYSTEM WITH THE SINGLE COLOR LASER
应用单色光的三维激光测速系统

A 3-D LDV system for measuring three velocity components by using a He-Ne laser has been presented. Four incident beams were arranged to be an isosceles triangle with a right angle and focused by a single front lens. Such a beam arrangement has been examined as a most efficient form of the light energy utilization. It is also well suited to measure the velocity profiles close to a wall even in the situations in existing two different layers which the incident beams have to penetrate through, In order to separate the three velocity components, both the frequency and polarizing separation techniques were used. The accuracy of on-axis velocity component was particularly considered both for mean and turbulent velocity measurements. Some methods for improving the measured accuracy were suggested. The 3 D mean and turbulent velocity distributions behind a bluff body with a slanted base were also obtained simultaneously by using this system.