Measurement of Velocity Fluctuations and Overpressure of Spherical Shock Wave in Grid Turbulence

Abstract

Velocity fluctuations of grid turbulence and overpressure of spherical shock wave are measured simultaneously in wind tunnel experiments. The experiments are conducted for four different conditions of grid turbulence, where the turbulent intensity and the length scales are different. Probability density functions (PDFs) of the velocity fluctuation and the peak-overpressure fluctuation measured on the wall are calculated in each experimental condition, and both follow the Gaussian profile. In this study, the instantaneous spatial distributions of turbulent velocity are estimated with the Taylor hypothesis. Correlation coefficients are calculated for the peak-overpressure fluctuation and the spatial distribution of the low-pass filtered turbulent velocity fluctuation to evaluate the relation between them. The positive correlation is found for the velocity fluctuation at the location away from the wall. The correlation calculated for a wide range of the cutoff length shows that the turbulent motions of the order of the integral length scale have large influences on the peak-overpressure fluctuation.