Generation of Gravity-Capillary Wind Waves by Instability of a Coupled Shear-Flow

The theory of surface wave generation, in viscous flows, is modified by replacing the linear-logarithmic shear velocity profile, air, with a model which links smoothly linear and logarithmic layers through buffer layer. This profile includes effects air flow turbulence using damped mixing-length model. In water, an exponential used. It shown that this coupled shear-velocity gives better agreement experimental data than linear-logarithmic, non smooth (in air)–exponential water), widely used literature. We also give new insights on retrograde modes are Doppler shifted at air-sea interface, namely threshold value current for occurrence second unstable mode.