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 <i>D</i> were obtained. This made it possible to carry out an initial verification of the available theoretical results in terms of the dependence of <i>D</i> on various parameters. To estimate <i>D</i> 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 <i>D</i>, 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 <i>z</i> is the depth of measurements. The issues of the measurements conduction and methods of comparing a theory with an experiment are discussed.