Investigation of Bias Errors in Laser Doppler Velocimeter Measurements

摘要

The problem of velocity bias laser Doppler Velocimeter (LDV) measurements made with counter type (burst) signal processors in turbulent flows was investigated. By using a signal processing technique which allowed velocity samples to be taken either randomly or at equal time intervals, the magnitude of the velocity bias was directly measured under various flow conditions. Using this technique, the validity of the one-dimensional velocity weighting correction of McLaughlin an Tiederman was investigated and found to be useful only at turbulence intensities below about 20 percent. Incomplete signal bias was also investigated and found to cause serious errors in unshifted LDV measurements. However, this bias may be virtually eliminated by frequency shifting. (Author)