文摘
Unlike the pier scour in bridge waterways, the local scour at offshore monopile foundations should take into account the effect of wave-current combination. Under the condition of wave-current coexistence, the water-soil interfacial scouring is usually coupled with the pore-pressure dynamics inside of the seabed. The aforementioned wave/current-pile-soil coupling process was physically modeled with a specially designed flow-structure-soil interaction flume. Experimental results indicate that superimposing a current onto the waves obviously changes the pore-pressure and the flow velocity at the bed around the pile. The concomitance of horseshoe vortex and local scour hole around a monopile proves that the horseshoe vortex is one of the main controlling mechanisms for scouring development under the combined waves and current. Based on similarity analyses, an average-velocity based Froude number (Fr a) is proposed to correlate with the equilibrium scour depth (S/D) at offshore monopile foundation in the combined waves and current. An empirical expression for the correlation between S/D and Fr a is given for predicting equilibrium scour depth, which may provide a guide for offshore engineering practice.