Dissipation Rate of Turbulence in a Water Layer under Wind Waves Based on Data of a Laboratory Experiment

Abstract

The aim of this work is to obtain estimates and parameterization of the dissipation rate of the turbulence kinetic energy (TKE dissipation), ε, induced in the upper water layer by the presence of wind waves at the surface. For this purpose, data from the laboratory measurements of the wind waves and three components of currents at six horizons in the upper water layer and four different winds are used. The measurements are performed in the wind-wave channel of the Institute of Applied Physics, Russian Academy of Sciences (IAP RAS) [1, 2]. It is established that, for most horizons, Kolmogorov-type ranges with the property \({{S}_{{Uz}}}(f) \propto {{f}^{{ - 5/3}}}\) are clearly seen in the frequency spectra \({{S}_{{Uz}}}(f)\) for the vertical velocity component U_z of the flow induced by wind and waves. Using the algorithms described in [3, 4], this fact allows us to obtain estimates of the TKE dissipation at the corresponding horizons and then establish the dependence of ε on the friction velocity \({{u}_{*}}\), the height of waves at the surface a₀, the peak frequency of the spectrum ω_p, and the depth of the horizon z. An analysis of the results (according to the available data) makes it possible to propose a parameterization of the form ε ≈ 0.00025\(u_{*}^{3}{{a}_{0}}/{{z}^{2}}\) for which a physical interpretation is proposed.