Experimental study on the solitary wave-current interaction and the combined forces on a vertical cylinder

Abstract Wave-current interaction affects both wave characteristics and current properties and therefore the combined forces on coastal structures. In the first part of this paper, a series of experiments on the solitary wave-current interaction are conducted to investigate how the wave height and water velocity are affected by the wave-current interaction. Then, a vertical cylinder, widely used as the foundation of coastal structures, is mounted into the wave flume. A series of experiments on the solitary wave-current interaction with the cylinder are carried out to investigate the combined flow-induced forces. The experimental results indicate that: 1) when solitary wave travels with following currents (current travels with the same direction of the solitary wave), wave height decreases with increasing current velocity. The effect of following current on wave height reduction is more significant for waves with smaller original wave height and in deeper water depth. When traveling with opposing currents (current travels with the opposing direction of the solitary wave), wave height does not vary monotonically with current velocity but shows an increase followed by a decrease. 2) When a solitary wave travels with following currents, the water velocity near still water level is equal to the linear superposition of water velocity of wave-alone and current-alone. 3) A nonlinear superposition method is suggested to predict the combined solitary wave-following current induced forces.