Influence of Currents on the Breaking Wave Forces Acting on Monopiles over an Impermeable Slope

It is known that the wave breaking process is significantly affected by a current, but little attention has been paid to the effect of wave–current interaction on the breaking wave forces acting on a monopile. This study presented a total of 88 flume tests, among which solitary and regular breaking waves were generated with a following current. The waves propagated over an impermeable slope and induced impulsive loads on a vertical monopile. The moments on the monopile were measured utilizing a high-precision load cell, and the effect of current velocities on the peak moment was analyzed. Test results indicate that there was an obvious nonlinear effect between breaking waves and a following current. For solitary waves, a following current accelerated the breaking process, leading to an increase by 274.21% at maximum in breaking wave forces. However, for regular waves, both the wave heights and the reversing flow were restricted with the increasing velocity of a following current, delaying the wave breaking process; under the regular test conditions, the moment on the pile decreased by 65.25% at maximum.