Turbulence Statistics for Jet Noise Source Modeling from Filtered PIV Measurements

Abstract

Time-resolved, particle image velocimetry was used to measure the velocity fluctuation field at three locations along the lipline of two subsonic jets. The time history data within these fields were filtered in the time domain using empirical mode decomposition to produce two signals from the velocity fluctuation measurements. One signal was for the low-frequency, large-scale turbulent eddy component of the velocity fluctuations and represented the computed results of a large-eddy simulation. The other signal was for the high-frequency, small-scale turbulent eddy component of the velocity fluctuations. This represented the missing scales of a large-eddy simulation. The effect of filtering on the statistical properties of the velocity fluctuations relevant to jet noise prediction modeling were studied. Two-point, space-time, cross correlations were computed for the axial velocity fluctuations. Comparisons were made for the second- and fourth-order two-point correlations, the integral phase velocities, length scales, and time scales, and the frequency dependent phase velocities, length scales, and time scales between the total, large-scale, and small-scale velocity fluctuations.