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[MIS24-01] Balance of baroclinicity and restoring force due to stable temperature stratification in developing horizontal convection in a finite fluid layer
Keywords:Horizontal convection, Temporal evolution, Stable temperature stratification
Convection driven by a temperature gradient along a horizontal surface at the same level is termed horizontal convection and plays important roles in various fluid motions on the Earth, e.g. oceanic flows, atmospheric flows, liquid metal flows inside the outer core. Conventionally, horizontal convection has been studied on its equilibrium state, i.e. a flow state after a sufficiently long time for thermal diffusion. Both buoyancy and baroclinicity dominate the equilibrium horizontal convection. By contrast, during a temporal evolution from a certain initial state toward an equilibrium state, effect of restoring force becomes prominent instead of that of the buoyancy. The developing horizontal convection has been scarcely discussed, and it is worth investigating.
In this study, we aim to identify the contribution of stable temperature stratification on flow characteristics of developing horizontal convection, where the stratification relaxes with time. Visualization experiments were performed adopting a rectangular vessel where differential heating is imposed at the top and other boundaries are thermally insulated. We could observe formation of circulating flows owing to the baroclinicity of the horizontal temperature gradient. Using particle tracking velocimetry, various flow characteristics, e.g. stream functions, thickness of circulating flows, total kinetic energy, were quantified. It was found that the degree of stratification becomes a primary parameter determining the flow features of developing horizontal convection. This finding extends the conventional scalings of Rayleigh number applicable in the equilibrium state by adding the stratification parameter even in the developing state.
In this study, we aim to identify the contribution of stable temperature stratification on flow characteristics of developing horizontal convection, where the stratification relaxes with time. Visualization experiments were performed adopting a rectangular vessel where differential heating is imposed at the top and other boundaries are thermally insulated. We could observe formation of circulating flows owing to the baroclinicity of the horizontal temperature gradient. Using particle tracking velocimetry, various flow characteristics, e.g. stream functions, thickness of circulating flows, total kinetic energy, were quantified. It was found that the degree of stratification becomes a primary parameter determining the flow features of developing horizontal convection. This finding extends the conventional scalings of Rayleigh number applicable in the equilibrium state by adding the stratification parameter even in the developing state.