An experimental study on thermal circulation driven by horizontal differential heating

Abstract

Circulation driven by horizontal differential heating is studied, using a double-walled Plexiglas tank $(20 \,{\times}\, 15\,{\times}\, 2.5$cm$^3$) filled with salt water. For instances of heating/cooling from above and below, results indicate that there is always quasi-equilibrium circulation. In contrast to most previous results from experimental/numerical studies, circulation in our experiments appears in the form of a shallow cell adjacent to the boundary of thermal forcing. The non-dimensional stream-function maximum confirms the 1/5-power law of Rossby, $\Psi\,{\sim}\,Ra^{1/5}_L$. Dissipation rate measured in the experiments appears to be consistent with theory.

For cases of heating/cooling from a sloping bottom, circulation is similar to cases with a flat bottom; circulation is strong if heating is below cooling, but it is rather weak if heating is above cooling. Nevertheless, circulation in all cases is visible to the naked eye.