| An existing Point Doppler Velocimeter (pDv) has been modified in an effort to improve the RMS velocity results. Improvements have been made by reducing the probe volume size by focusing the incident laser beam, thereby reducing the effects of spatial averaging on the mean and RMS velocity measurements.; In particular, the PIN photodetectors used previously, were tested using the reduced probe volume, and were then replaced by high-gain, high signal-to-noise ratio large area avalanche photodetectors (APD's).; Comparisons have been made between the data acquired and hot wire data obtained on the same jet flow, as well as data obtained in previous pDv research and two theoretical profiles. Good agreement was found with the mean and RMS velocity hot wire results at the exit of the jet, and the RMS velocities downstream have been improved as well. (Abstract shortened by UMI.)... |
