Space–time characteristics of the wall shear-stress fluctuations in a low-Reynolds-number channel flow

A database obtained by direct numerical simulation of turbulent channel flow is used to compute the frequency/wave number spectra of the wall shear-stress fluctuations. Auto- and cross-correlations of the wall shear-stress and pressure fluctuations are obtained in space and time domains. The convection velocities as a function of frequency, wave number, and spatial and temporal separations are calculated. The overall convection velocities of wall shear-stress fluctuations for the most energetic structures are obtained and the validity of Taylor’s hypothesis is confirmed.