Momentum and Energy Exchange in Misaligned Wind-Wave Condition

Surface gravity waves traveling at an oblique angle to the wind are common in the ocean, particularly during storms. Understanding the momentum and energy exchange between misaligned wind and waves is crucial for wave forecasting and the effective control of offshore wind turbine platforms. Here, two-phase Direct Numerical Simulations (DNS) with adaptive mesh refinement is employed to investigate wind–wave interactions across a range of wave steepnesses (ak), friction velocity to phase speed ratios (u∗​/c), and wind–wave misalignment angles. Precursor simulations, performed with misaligned wind over a fixed wave field, confirm previous scaling for pressure (form drag) and shear (skin drag) induced forcing. The converged flow fields of precursor runs are then used as the initial condition for fully coupled simulations in which both the airflow and the wave field evolve dynamically without modeling assumptions. In fully coupled simulations, the skin drag of misaligned wind over moving wave is related to relative aligned component of wind velocity to wave phase velocity. Energy input from pressure dominates that from shear stresses. Mean wind velocity and turbulence structures are compared with previous perturbation theories. Two-dimensional momentum budget is also discussed.