Flow recovery in the wake of a suspended flat plate

The flow field behind a flat plate suspended in an open channel is investigated using LDV. The formation of a gap between the plate and channel bed produces a flow that is different from the flow around a wall-mounted bluff body. The gap can be perceived as an end condition of the plate that suppresses the formation of the horseshoe vortex and modifies the interaction between the plate and the wall bounded flow. As the flow plunges under the plate through the gap, a wall jet is formed. As the wall jet grows and interacts with the wake-like flow, the effect of the wall jet diminishes with increasing distance downstream of the plate, beyond which the turbulent flow in the wake may be considered to be quasi-two-dimensional. Flow recovery is examined in terms of the mean velocity, turbulence intensity and quadrant decomposition. The present results indicate that the near-wall region of the mean flow recovers faster than the outer region. The turbulent intensities showed a similar tendency. The Reynolds shear stress distributions indicated full recovery while turbulence intensities did not recover completely, especially in the outer regions of the flow. However, a quadrant analysis reveals that at the last measuring station and away from the wall region, the flow is still being influenced by the disturbance generated in the wake region.