Stress above wind plus paddle waves: modelling of a laboratory experiment
Résumé
A Wind-Over-Waves Coupling (WOWC) model is used to simulate a laboratory experiment and to explain the observed peculiarities of the surface stress distribution above a combined wave field: wind generated plus monochromatic paddle waves. Observations show the systematic and significant decrease in the stress as the paddle wave is introduced into the pure wind wave field. With the increase of the paddle wave steepness the stress level returns to the stress level characteristic of the pure wind waves. Further increase in the paddle wave steepness augments the stress further. The WOWC model explains this peculiarity of the stress distribution by the fact that the paddle waves significantly damp the wind waves in the spectral peak. The stress supported by these dominant waves rapidly falls when the paddle wave is introduced, and this decrease is not compensated by the stress induced by the paddle wave. With further increase in the steepness of the paddle wave, the stress supported by dominant wind waves stays at a low level, while the stress supported by the paddle waves continues to grow proportional to the square of the steepness, finally exceeding the stress level characteristic of the pure wind wave field.