Stability of Rayleigh-Benard convection patterns in a rectangular container.

We report a study of the flow patterns associated with Rayleigh- Benard convection in rectangular containers of approximate proportions 10x5x1. Water and ethanol are studied at temperatures between 10C and 80C in order to span a range of Prandtl numbers from 2 to 20. The measurements include the range of Rayleigh numbers from the onset of convective flow to the onset of time dependence. Nusselt number measurements for this range of parameters are also presented.