Evaluation of methods for assessing spectra from laser Doppler velocimetry signals

Abstract

A critical evaluation is made of the spectral bias which occurs in the use of a laser Doppler velocimeter (LDV). In order to accommodate the highly turbulent random sampled LDV data, a doubly stochastic Poisson process is generated. Four well-known processing algorithms, i.e., the direct transform (RG), the transit-time weighting method (TW), the sample-and-hold method (SH), and the modified Shannon sampling technique (SR), are evaluated and compared with the theoretical spectra for various sampling and flow conditions. Assessment of these algorithms is made for varying data densities (0.05 ≤ d.d. ≤ 5.0) and turbulence levels (t.i. = 30% and 100%). Furthermore, the effects of the Reynolds stress coefficients and of the transversal standard deviations on the spectral bias are examined. © 1995.