Experiments on the turbulent wake of a flat plate in a strong adverse pressure gradient

The wake of a flat plate was subjected to an adverse pressure gradient of sufficient strength to cause local mean-flow reversal. The mean-flow and turbulence statistics were determined with a three-component laser Doppler anemometer. The experimental data were used to determine balances of the momentum equation and the turbulence kinetic-energy equation. The latter showed that the production of turbulence kinetic energy remained at a constant high level whereas the dissipation decreased when moving past the trailing edge into the wake. As a consequence, the turbulence kinetic energy becomes very high in the wake. Spectral density functions measured at various locations in the wake indicate that turbulence kinetic energy accumulates in the very low-frequency range. It is suggested that this is due to the formation of unsteady roll cells in the trailing-edge region.