On the decay law of quasi-two-dimensional turbulence

Laboratory measurements of decaying quasi-two-dimensional turbulence in thin fluid layers with various depths have been performed. It has been shown that decay at large Reynolds numbers corresponds to a non-linear bottom friction with the coefficient satisfying the law $\lambda\sim(\nu/h^2)^{1/2}|K|^{1/4}$ following from theoretical estimates, where $K$ is the Okubo-Weiss function depending on the enstrophy and degree of ellipticity of vortices. It has been shown that the structure of the flow changes in the decay process.