Biasing correction for individual realization of laser anemometer measurements in turbulent flows

TLDR

In turbulent flows, laser anemometer histograms obtained in individual realization mode are biased because faster velocity periods bring a larger fluid volume and more scattering centers, while slower periods bring fewer. The correction applies a weighting function equal to the inverse of the instantaneous velocity vector to compensate for this bias. Model analysis indicates that using only the streamwise velocity component for weighting is sufficient for many flow situations.

Abstract

In turbulent flow situations the histograms constructed in the individual realization mode of laser anemometry are biased. The biasing occurs because a larger than average volume of fluid, and hence a larger than average number of scattering centers, pass through the probe volume during periods when the velocity is faster than the mean. Similarly, a smaller volume of fluid and a smaller number of scattering particles pass through the probe volume during periods when the velocity is slower than the mean. The proper weighting function needed to correct the biased data is the inverse of the instantaneous velocity vector. However, an analysis using turbulent flow models show that corrections based only upon the streamwise component of the velocity vector are adequate for many flow situations.