Wave-current interactions: A review of some problems

Methods for calculating the interaction of water waves with a vertically varying current which is steady and uniform in the horizontal plane are assessed using experimental evidence on wave-current interactions. It is shown that the effect of current shear is important in determining the kinematics for the waves. Linear superposition of waves and currents is generally inadequate to describe their interaction. Doppler shift in wave frequency due to the current should be allowed for. For small amplitude waves, perturbation theory gives good agreement with laboratory measurements. For finite amplitude waves further comparisons between theory and experiment need to be carried out to check the theoretical results. The correct specification of the current profile in the calculations needs to be investigated.