A study on flow past a suspended bluff object in an open channel

Detailed velocity and erosion measurements in the near wake of a flat plate with a gap between the plate and the channel bed in an open channel are pr esented. A "wall jet" like flow (confined to the wall region) is observed t o interact with the wake flow behind the body. Two axial stations downstrea m of the body were chosen to obtain the velocity profiles in the near wake region. The span-wise velocity profiles across the wake at two distances fr om the channel bottom were also obtained. This yielded information in the d evelopment of the "wall jet" like flow and also provided some sense of the velocity components in the near wake. At mid-section of the gap, the stream wise mean velocity attains its peak value at one body width. The velocity m easurements across the wake exhibit the cause of erosion. Erosion measureme nts were simulated on an erodible sand bed of D-50 = 0.59 mm grain size. Th e erosion patterns obtained show symmetry about the centerline of the plate . A ripple-like pattern was observed with deeper scour holes generated towa rds the edge of the wake. Flow separations from the lower corners and the s ides of the plate account for this typical nature of the erosion pattern.