Three-Dimensional Flow Characteristics within the Scour Hole around Circular Uniform and Compound Piers

Abstract

AbstractThe experimental observations are presented on flow patterns and turbulence characteristics measured by an acoustic Doppler velocimeter within the developing (transient stage) scour hole around circular uniform and compound piers. Four series of experimental runs were conducted under the clear-water approach flow conditions. One experimental run was conducted around a uniform circular pier of diameter 114 mm, whereas the other three runs were conducted around a circular compound pier of diameter 114 mm and footing diameter 210 mm. In the series with a circular compound pier, the top surface of the footing was placed at three different elevations with respect to the general level of the channel bed, i.e., above the bed level, at the bed level, and below the level of the channel bed. Detailed measurements are presented on components of time-averaged velocity, turbulence intensity, and Reynolds shear stress around the pier in radial planes at 0°, 90°, and 180° from the flow axis. Flow structure aroun...