Flow Velocimeter with Wide-Stripe Semiconductor Laser

A semiconductor laser with a wide active stripe was utilized as the power source of a laser 2-focus velocimeter. The focus was expanded to about 0.2mm wide to form the two parallel focal planes. The backscattered light from seeding particles was detected by photodiodes, and the time-of-flight between two foci was counted by means of a digital clock. The flow velocity was measured in a circular jet stream, and the results were compared with those measured simultaneously by Pitot tube. After checking the accuracy of measurements, the blade-to-blade distribution of velocity and flow angle were measured at the exit of a centrifugal impeller to confirm the applicability of the semiconductor-L2F with band focus.