Turbulence spectra from individual realization laser velocimetry data.

Two techniques - a modified correlation method and a direct transform method - were evaluated for the use in making spectral estimates from randomly sampled random data (such as turbulence data obtained with an individual realization laser Doppler velocimeter (LDV)). The effect of 'bad' points(which usually appear randomly in actual LDV data sets) on the spectral estimates was studied. Necessary modifications and extensions to the techniques were studied and determined based on studies using simulated data with known spectral characteristics. The direct transform method was found to have certain advantages over the correlation method. From the LDV measurements taken in a simulated coal fired magnetohyrodynamic flow field, major differences in turbulence spectra obtained from the two methods are observed in the region immediately downstream of the combustion instabilities. Spectra are reported for three axial positions, and comparisions with classic turbulenct pipe flow data are presented. (A)