ANGULAR BIAS ERRORS IN 3-COMPONENT LASER VELOCIMETER MEASUREMENTS

For three-component laser velocimeter systems, the change in projected area of the coincident measurement volume for different flow directio ns will introduce an 'angular' bias in naturally sampled data. In this study, the effect of turbulence level and orientation of the measurem ent volumes on angular bias errors was examined. The operation of a ty pical three-component laser velocimeter was simulated using a Monte Ca rlo technique. Results for the specific configuration examined show th at for turbulence levels less than 10 percent no significant bias erro rs in the mean velocities will occur and errors in the root-mean-squar e (r.m.s.) velocities will be less than 3 percent for all orientations . For turbulence levels less than 30 percent, component mean velocity bias errors less than 5 percent of the mean velocity vector magnitude can be attained with proper orientation of the measurement volume; how ever, the r.m.s. velocities may be in error as much as 10 percent. For turbulence levels above 50 percent, there is no orientation which wil l yield accurate estimates of all three mean velocities; component mea n velocity errors as large as 15 percent of the mean velocity vector m agnitude may be encountered.