Session Ch - Convection & Buoyancy.
ORAL session, Sunday, November 23
308, Moscone Center
Numerical simulations have been performed of turbulent, non-penetrative thermal convection at Ra = 2 \times 10^7, in which the lower boundary condition is one of constant heat flux, and the upper boundary is insulated. While the bulk temperature of the fluid increases linearly with time, the spatially-averaged temperature profile exhibits a time-invariant behavior along the vertical coordinate. The numerical study has replicated earlier PIV measurements of the same flow, in a 76.2~mm thick layer of water at an aspect ratio of 6.6. Ongoing simulations are focused on the phenomenon of ``mean-flow'', i.e., a global flow whose length scale is on the order of the horizontal dimension of the flow domain, which has been reported in a number of experiments. We have artificially created such a mean-flow in our simulations by introducing a perturbation in the established flow; the perturbation comprises of an excess of heat flux, for a specified duration, along a narrow strip on the lower boundary, adjacent to one side wall. The magnitude and self-sustaining ability of the resulting mean-flow will be determined as a function of the excess heat-flux, its duration, and the container aspect ratio.