Developing horizontal convection against stable temperature stratification in a rectangular container

Abstract

The effect of background stable temperature stratification in the developing stage of horizontal convection is studied by conducting laboratory experiments. By imposing horizontally differential heating at the top of a layer of low-temperature water, both vertical and horizontal temperature differences are explicitly defined. In developing horizontal convection of the present study, the flow structures are driven only by the baroclinic torque produced by the horizontal temperature difference, and braked by the restoring force of stable temperature stratification. We thus defined a nondimensional stratification parameter, which represents the balance of the braking force and the baroclinic torque, in addition to the Rayleigh number. Various features of the flow structures, maximum velocity, stream function, roll thickness, circulation of the roll, total kinetic energy, and Reynolds number, which are quantified via particle-tracking velocimetry, are summarized in spaces of the two nondimensional parameters. In the developing horizontal convection, the quantified flow features are well organized by power laws of the nondimensional parameters. The finite domain of the fluid container augments the effect of the apparent braking force, and the bulk quantities of the roll structures are suppressed by the stable temperature stratification. These results are the evidences for the significance of the nondimensional stratification parameter in the developing horizontal convection, unlike thermally equilibrated horizontal convection conventionally considering destabilizing thermal buoyancy as the primary driving force.