Experimental study of turbulent Poiseuille-Couette flow

Results from the experimental study of fully developed turbulent plane Poiseuille-Couette flow (PCF) are presented. This study provides information that improves the physical descriptions of previous experimental works and sheds light on turbulence phenomena reported at low to moderate Reynolds numbers. Molecular tagging velocimetry (MTV) is employed for the first time on gas PCFs over the Poiseuille and Couette flow Reynolds number ranges of 3500 < Re-d< 9700 and -1700 < Re-c<+1700, respectively. MTV has allowed the measurement of instantaneous velocity profiles at a much higher resolution than previous single point techniques. Results include a locally negative production of streamwise turbulence near the forward moving wall, and a noticeable effect on intensities in the core flow region and near the moving wall. It has been found that the so-called geometry effect does play a role in the exchange of fluid motions between the channel walls at low Re-d. This effect is amplified when one of the walls is put into motion. Results indicate that the exchange of disturbances is mainly driven by the more energetic motions or active motions originating at the high stress wall. These disturbances are convected towards the low stress wall and impinge on its surface. This can lead to a localized region of negative turbulence energy production. (C) 2000 American Institute of Physics. [S1070-6631(00)01004-7].