Design and testing of a high data rate instantaneous laser doppler velocity probe

An Instantaneous Laser Doppler Velocimetry (ILDV) probe is designed, built, and tested. The probe is capable of measuring a single component velocity data at a rate as high as two megahertz. The probe can be employed in high-speed and unsteady flows, especially where high data capture rate is needed such as in shock tubes, high-speed wind tunnels, and pulse detonation engines. However, the probe use is not restricted to only high speed flows. The probe, as designed, requires the flow direction to be known as it cannot discern the flow direction. Light scattered by particles illuminated by a laser beam in the flow is collected via backscattering. This light is transmitted to a breadboard housed in a container designed to insulate the system from sound, light, and vibration. The transmitted light is collimated and passed through a Michelson interferometer. Doppler frequency information contained in the beam is converted to light intensity variation using polarization optics. Two photomultiplier tubes are used to detect the light intensity variations. The output of the PM tubes are acquired using a high-speed data acquisition board, and analyzed in a PC to determine the flow velocity. (Published By University of Alabama Libraries