Linear dynamics of wind waves in coupled turbulent air-water flow. Part 2. Numerical model

A numerical model of the interaction between wind and a small-amplitude water wave is developed. The model first calculates the turbulent flows in both the air and water that would be obtained with a flat interface, and then calculates linear perturbations to this flow caused by a travelling surface wave. Turbulent stresses in the base flow are parameterized using an eddy viscosity, while those in the perturbed flow are parameterized using a new damped eddy viscosity model which has been proven to accurately capture the physical processes producing the asymmetric pressure that leads to form drag and also wave growth. The developed numerical model suggests that the wave-induced flow in the water is irrotational except in an extremely thin interface layer, where viscous stresses are likely to be important as turbulent stresses.