Measurement and interpretation of space-time correlation functions and derivative statistics from a rotating hot wire in a grid turbulence

Abstract

A family of autocorrelation functions and derivative statistics are measured by a rotating hot wire in a grid turbulence. The autocorrelation functions, at various probe radii and speeds, can be rescaled with the probe effective velocity suggesting that Taylor's hypothesis is satisfied. The effects of the random convecting speed and the temporal change which would violate the hypothesis are however effectively removed in computing the autocorrelation functions. For the derivative statistics, it is shown that the eulerian temporal derivative statistics can be determined from the time derivative statistics measured by the moving probe at two different speeds based on the principle of Galilean invariance. The Reynolds number dependence of the eulerian temporal derivative mean square values suggests that the main contribution comes from the nonlinear acceleration terms in the limit of high Reynolds number.