Drag prediction over steep sinusoidal wavy surfaces

A parametrization of the form drag due to airflow over sinusoidal wavy surf aces in the presence of significant flow separation is investigated; it is based on a bluff-body analogy. To this aim, the results of large-eddy simul ations carried out for various Reynolds numbers and wave slopes are used, t ogether with the data from experiments and other simulations available in t he literature. It is shown that, as a first approximation, the drag coeffic ient may be considered independent of the wave slope and Reynolds number. T he value obtained here for rigid sinusoidal waves is close to that computed for wind-ruffled breaking paddle waves. (C) 2001 American Institute of Phy sics.