Experimental study on scour around a composite bucket foundation due to waves and current

Abstract Local scour around foundations is a hot research topic in ocean engineering, especially for shallow composite bucket foundations. In this study, a physical model was developed for the scour induced by waves and current around a composite bucket foundation. Foundation models with scales of 1:40 and 1:60 were placed in a flume, and the scour process was monitored at eight points arranged evenly and symmetrically along the model circumference. The scoured topography was investigated in detail under different wave and current conditions, and the maximum equilibrium scour depths were compared. The experimental results showed that the combined wave–current condition induced a greater scour range than the wave-only or current-only condition, but it did not necessarily induce a greater equilibrium scour depth than the current-only condition. In contrast to the current-induced scour, the combined wave–current and wave-only conditions induced obvious scour pits in the front of and close to the foundation. The effects of dimensionless parameters such as the Keulegan–Carpenter number ( K C ), ratio of velocities ( U c w ) and Froude number ( F r a ) on the maximum equilibrium scour depth were considered.