Comparison of Data from the Transit Time Velocimeter with Other Systems Now in Use for velocity Measurements

This report discusses the principles of operation of the laser transit anemometer LTA, developed and constructed under this contract, and its use with a photon correlator. AEDC developed an electronic processor for fringe laser velocimeter systems. A test was conducted in a free jet with a stationary Mach disc to compare the sensitivity of the new processor with the older Model 8 burst-counter processor with respect to small-particle relaxation behind a shock front. The LTA combined with the photon correlator produced accepable velocity data. Flare light can be most satisfactorily rejected by well-considered geometrical design and attention to optical components. The transit configuration allows at least an order to magnitude improvement in the proximity to walls at which good measurements may be made. The capabilities of the transit system to look at smaller particles and measure stresses by spot radiation are especially useful close to walls.