Theory and implementation of laser velocimeter turbulence spectrum measurements
Abstract
A laser velocimeter turbulence spectrum system that provides reliable power spectra estimates is described. The theory of the approach is based on reconstructing the autocorrelation function (ACF) of the fluid velocity directly from the LV data, bypassing the conventional requirement of the complete velocity time history. With certain assumptions on the particle arrival statistics it may be shown that it is possible to perform this reconstruction at arbitrarily low particle arrival rates. The result is a biased estimate of the velocity ACF which converges as the amount of data processed is increased. By proper system design, the biases in the ACF estimate may be reduced to an acceptable level. A spectrum is then obtained from the ACF by performing a weighted discrete Fourier transform. The resulting equations for the ACF and spectrum estimators have been realized using a PDP8E computer to demonstrate the feasibility of this approach. Accurate spectra have been obtained from both hot and cold jets.
 Publication:

2nd International Workshop on Laser Velocimetry, Volume 1
 Pub Date:
 1974
 Bibcode:
 1974lave....1...47S
 Keywords:

 Flow Velocity;
 Laser Applications;
 Power Spectra;
 Turbulent Jets;
 Velocity Measurement;
 Autocorrelation;
 Data Processing;
 Error Analysis;
 Fluid Mechanics;
 Poisson Equation;
 Spectrum Analysis;
 Subsonic Flow;
 Transonic Flow;
 Fluid Mechanics and Heat Transfer