Direct Measurement of Turbulent Diffusion Induced by Waves in a Tank
Using the laboratory experiments carried out in a wind-wave tank, estimates of the turbulent diffusion coefficient D were obtained. This made it possible to carry out an initial verification of the available theoretical results in terms of the dependence of D on various parameters. To estimate D using the Einstein formula, we used measurements of the spreading rate of an ink blot in the water layer under the waves. Comparison of the obtained estimates with a set of model parameterizations for D, as functions of parameters of the system, has shown that in the presence of wind waves, the statistical advantage has the parameterization of the kind $D \propto {{u}_{*}}{{a}_{0}}\delta $, and in the presence of mechanical waves does $D \propto {{a_{0}^{3}{{f}_{p}}} \mathord{\left/ {\vphantom {{a_{0}^{3}{{f}_{p}}} z}} \right. \kern-\nulldelimiterspace} z}$, where ${{u}_{*}}$ is the friction velocity, ${{a}_{0}}$ is the amplitude of the waves at the surface, ${{f}_{p}}$ is the peak frequency of the wave spectrum, $\delta $ is the wave steepness, and z is the depth of measurements. The issues of the measurements conduction and methods of comparing a theory with an experiment are discussed.