Abstract
Characteristics of the momentum and scalar transfer processes of the airflow over a train of waves moving at a constant speed are investigated using a direct numerical simulation. We simulate the flow for various wave ages (c/u* = 0, 2, 4, 5, 6, 8, 10, 12, 16 and 20), where c is the phase speed of the wind wave and u* is the friction velocity on the wave surface. The results show that the vertical gradients of both the mean velocity and the mean scalar depend on the wave age at kz < 1.5 due to the effects of the wave-induced momentum flux and wave-induced scalar flux. Correspondingly, the drag coefficient and scalar exchange coefficient strongly depend on the wave age. The wave age dependence of the scalar transfer coefficient is approximately the same strength as that of the drag coefficient.
