ABSTRACT

The study is aimed at investigating the mean flow and turbulence in scour geometry developed around a short circular cylinder placed on a sand bed transverse to the flow. The scour is caused by generation of vortex on the upstream side of the obstacle. Sand grains eroded by this vortex, are deposited on the downstream side of the obstacle as wakes. The turbulent flow across the scour hole was measured in a laboratory flume using an Acoustic Doppler Velocimeter (ADV). The distributions of mean velocity components, turbulent intensities, Reynolds shear stress and associated burst-sweep cycles to the total Reynolds shear stress at different positions of the hole are presented. A theoretical model of probability density function of momentum flux variable is employed to verify the quadrant threshold technique used for conditional statistics (Nakagawa and Nezu, 1977; Raupach, 1981). The theoretical model shows good agreement with the experimental estimates.