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 0.2 mm 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.