Laboratory Experiments on Thermo-Chemical Convection at High Rayleigh and Prandtl Numbers

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9804904RichardsConvection in the mantles of terrestrial planets is extremely vigorous (high Rayleigh number), and it occurs with negligible influence from inertial forces (zero Reynolds number or infinite Prandtl number). Although modern computer models now approach this fluid dynamic regime, almost no relevant laboratory experiments have been performed. The P.I.'s propose to construct a very large tank to study convection at high Rayleigh and Prandtl numbers, using fluids with strong temperature-dependence of viscosity and differing densities to simulate a variety of processes considered important in the Earth's internal dynamics. These processes include mixing of various geochemical components by mantle convection, and the influence of convection on continental dynamics. They will employ new digital video imaging techniques to measure the flow and temperature fields in the tank, simultaneously producing a series of films illustrating the various fluid dynamic processes involved in mantle convection. They also propose to carry out direct comparisons of laboratory and numerical models of convection in order to provide much better experimental verification of results from large-scale computation.