The vortex motion around an obstruction in a movable bed is extremely complex. To model pier scour as a function of the size and strength of the vortex at the base of the pier, it may be desirable to characterize the strength of the vortex under various conditions in terms of a measurable quantity. The vortex strength is characterizedin terms of stress at the base of a bridge pier as a function of pier width and scour depth. A flume experiment was conducted to determine indirectly the relative magnitudes of shear stress for various pier diameters and scour depths using a sediment that is uniform in size and shape. One advantage of the experiment method is that no instrumentation was required in the scour hole; therefore, there was nointerruption of the flow pattern around the pier or within the scour hole. From the data, a relationship between the shear stress and the equilibrium scout depth may be developed
Abstract