Numerical and experimental simulations of wind effect on rogue waves
Résumé
Rogue wave generation can be explained on the basis of spatio-temporal focusing concept. The paper reports on a series of numerical simulations based on a BIEMmethod and their comparison with experiments. The modulated wave trains are numericallygenerated by a paddle and the wind effect is described by the introductionof wind-induced current. The time-variable frequency of the paddle is chosento produce a rogue wave (due to spatio-temporal focusing) at a given fetch. Numericalsimulations are performed for different values of wind-drift current (us =0, 20, 25, 30, 40, 50cm.s−1), corresponding to the experimental values of wind speed(U = 0, 4, 5, 6, 8, 10m.s−1). It is shown that the shift of the focusing point increasesas u2s, as predicted theoretically (Pelinovsky & Kharif, 2005). A spreading of the focusingarea and a weak decrease of the rogue wave amplification are observed asthe wind speed increases. Experiments showed that the amplification increases as thewind speed increases (Giovanangeli & al., 2004). This disagreement suggests that theamplification of the rogue wave may be due the direct effect of the wind on the freesurface which is not taken into account in the numerical model.