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 flo w is used to compute the frequency/wave number spectra of the wall shear-st ress fluctuations. Auto- and cross-correlations of the wall shear-stress an d pressure fluctuations are obtained in space and time domains. The convect ion velocities as a function of frequency, wave number, and spatial and tem poral separations are calculated. The overall convection velocities of wall shear-stress fluctuations for the most energetic structures are obtained a nd the validity of Taylor's hypothesis is confirmed. (C) 1999 American Inst itute of Physics. [S1070-6631(99)03510-2].