Features of Wind Wave–Induced Turbulence in Water According to Measurements in a Wind-Wave Tank

Three velocity components u i ( i = x , y , z ) have been measured in a wind-wave tank at three levels in water in the presence of wind waves. The degree of anisotropy of a wind wave–induced turbulence and the rate of its dissipation ε are estimated versus system parameters. For this, standard deviations σ i and the frequency spectra S i ( f ) are calculated for the components of the flows measured, as well as σ iF and S iF ( f ) for the turbulent components of the flows with filtered wave motions. The following is ascertained: (a) the turbulence is not isotropic; (b) σ x > σ y > σ z and σ xF > σ yF > σ zF ; and (c) more than 70% of the kinetic energy is contained in the turbulent components of flow fluctuations. The spectra of the horizontal velocity components are similar in shape and intensity. In the frequency range below wave spectrum peak frequency f p , spectra S i ( f ) of all the flow components decay by the power law with the exponent equal to –1.7 ± 0.1. In the frequency range f > 2f p , spectra S x ( f ) and S y ( f ) are close in intensity and their decay obeys the same law, but the intensities of the spectra of the vertical component S z ( f ) are almost an order of magnitude weaker and spectra S z ( f ), in the presence of a power-law tail, decay by the law –2.0 ± 0.1. These segments of the spectra are interpreted as analogs of the Kolmogorov spectra. The intensity of spectra S z ( f ) was used to estimate the turbulence dissipation rate ε. Semiempirical parameterizations of the dependences of σ iF and ε on wave parameters and the measuring depth are constructed; their differences from the known parameterizations and possible causes of features of the spectra S i ( f ) are discussed.