Computational Turbulent Shear Flows Over Growing And Non-Growing Wave Groups

A high-Reynolds-number second-order stress closure model is used to perform numerical simulations of the wind flow above different groups of waves. It is shown that the group profiles can change as the individual waves grow within its envelop due to the energy transfer between the wind and the group. The focus of this study is the behaviour of the critical-layer and the associated with "cat’s-eye" structures which are centred around the critical height, where the real part of the complex wave speed is equal to the mean flow velocity. It is also shown that the position and size of these structures depend on the wave age and the wave steepness. It is demonstrated that the larger these structures become, the greater disturbance of the wind flow above the wave groups appear. Also, the results obtained here demonstrate how the critical layer structures are asymmetrical over the waves within a group because of the shear driven sheltering effect on the downwind side of the group. The results here complement the general review of wind-wave dynamics by Hunt & Sajjadi [1].