Richard R. Simons, Andreas G. Kyriacou


When applied to real engineering problems, mathematical models of combined wave-current flows usually assume that both wave and current properties remain in a quasi-steady state. Shear stresses and other flow parameters are calculated for instantaneous values of wave height and current strength, regardless of the changes being induced by tides, winds, or wave grouping. This paper describes tests carried out in a wave flume to investigate velocity profiles, bottom shear stresses and water surface characteristics under gradually developing flow conditions, such as those created when a group of waves is superimposed onto a pre-existing current or when a steady current is added to a train of regular waves. Results indicate that, at laboratory scale, the water surface characteristics adapt within a few wave periods to changes in superimposed waves or current, but that mean velocity profiles and shear stresses may take considerably longer to respond to the new flow conditions.


boundary layer; wave/current layer; boundary layer development

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