The effect of surface roughness induced by mean turbulent water flow on excitation of waves by wind*

Mean turbulent water current has a twofold effect on the excitation and evolution of waves in a laboratory wind-wave facility: it not only modifies the dispersion relation due to current-induced Doppler shift, but also results in surface roughness. The effect of both those phenomena on the variation with fetch of the wave field excited by wind blowing steadily along or against the wind is studied experimentally. Data on diverse wave parameters such as characteristic wave amplitudes, dominant frequencies, wave spectra, etc., are accumulated for a range of well-controlled operational conditions. A more complicated case of evolution in time and in space of waves generated by impulsively applied wind over an initially rough water surface in flowing water is studied as well. Interpretation of the accumulated experimental findings in the framework of Geva and Shemer¹ stochastic multiple harmonic approach sheds new light on the long-standing problem of identifying the mechanisms that govern generation of waves by wind.

¹M. Geva and L. Shemer (2022) A comprehensive approach to the problem of excitation of waves by wind: a theoretical model and experimental verification, Phys. Rev. Lettr. 128, 124501