Experimental Study of Flow Characteristics and Geometry of Scour Hole around Cylindrical Piers Subject to Wave and Current

Abstract

Scour is a significant contributing factor to bridge failures, and when a bridge fails, it totally or partially loses its serviceability, causing fatalities, delays in emergency transportation and evacuation efforts, and economic losses. The mechanism of scour in riverine environment is different from those in areas under wave action, that is, coastal, and lacustrine environments. A total of 38 experiments were conducted in the laboratory under wave-alone, current-alone, and waves–current combined conditions to investigate the flow pattern and geometry of scour holes around bridge piers. Under these conditions, different flow parameters were considered and the influence of these parameters on the scour hole geometry was observed. The results showed that the combination of wave and current produced scour depths larger than those of the wave-alone experiments but smaller than those created by the current. Particle image velocimetry was used to investigate the flow field around piers and observe changes in vortex characteristics due to the change in flow conditions. Finally, an attempt was made to relate the size and shape of vortices to the scour process. It was concluded that the strength of wake vortices, the relative direction of the flow and wave, and the distances of waves from the channel bottom influenced the scour geometry and the downstream deposition pattern.