Effect of the Current-Wave Angle on the Local Scour Around Circular Piles

This paper studies the effect of the wave front-current angle on the scour around a circular pile. An experimental study was carried out in the Coastal, Ocean and Sediment Transport (COAST) laboratory at the University of Plymouth (UK) using a single monopile of 0.125 m in diameter and an 8 m long by 1.5 m wide by 0.2 m high sand pit. The results obtained during the test campaign show the influence of the angle between waves and currents on both the maximum scour depth and the time scale of the process. Wave fronts partially aligned with current (65 degrees) produce deeper scour holes than perpendicular forcing conditions (90 degrees). Wave fronts partially against the current (115 degrees) produce less scour than any of the two previous scenarios. The addition of waves reduced the maximum scour depth, compared with the current-only case. The development of the scour hole was found to be more rapid when waves are added to the current, with 50% of the final scour achieved in half the time. The results show that wave direction relative to the current is an important component in scour prediction.