Scour around pile in combined waves and current

This paper presents the results of an experimental study on scour around a pile subject to combined waves and current. Irregular waves were used in the experiments, which were carried out both for codirectional waves and for waves propagating perpendicular to the current. The measured scour depth is plotted as a function of U-cw = U-c/(U-c + U-m) for various values of the Keulegan-Carpenter number KC in which U-c is the undisturbed current velocity and U-m is the maximum value of the undisturbed orbital velocity at the sea bottom. In the experiments, KC ranges from 5 to about 30 and U-cw from 0 to 1. The results show that the scour depth increases with increasing current component of the flow. The scour depth attains its steady-current value for U-cw > 0.7.