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Article Dans Une Revue Physical Review Fluids Année : 2020

Effect of current on wind-wave generation

Résumé

We investigate numerically the influence of currents on wind-generated surface deformations for wind velocity below the onset of regular waves. In that regime, the liquid surface is populated by small disorganised deformations elongated in the streamwise direction, referred to as wrinkles. These wrinkles are the superposition of incoherent wakes generated by the pressure fluctuations traveling in the turbulent boundary layer. In this work, we account for the effect of a current in the liquid, either longitudinal or transverse, by including a modified Doppler-shifted dispersion relation in the spectral theory previously derived by Perrard et al. [J. Fluid Mech. 873, 1020-1054 (2019)]. We use the pressure data from direct numerical simulation of the turbulent air flow to compute the surface deformation, and determine the wrinkle properties (size and amplitude) as a function of the liquid viscosity and current properties (surface velocity, thickness and orientation). We find significant modifications of the wrinkle geometry by the currents: the wrinkles are tilted for a transverse current, and show finer scales for a longitudinal current. However, their characteristic size is weakly affected, and their amplitude remains independent of the current. We discuss the implications of these results regarding the onset of regular waves at larger wind velocity. In this work, we introduce a new spectral interpolation method to evaluate the surface deformation fields, based on a refined meshing close to the resonance. This method, which can be extended to any dispersive system excited by a random forcing, strongly reduces the discretization effects at a low computational cost.
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Dates et versions

hal-03273645 , version 1 (07-05-2020)
hal-03273645 , version 2 (29-06-2021)

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C Nové-Josserand, S. Perrard, A Lozano-Durán, Michael Benzaquen, M. Rabaud, et al.. Effect of current on wind-wave generation. Physical Review Fluids, In press. ⟨hal-03273645v1⟩
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