Heat transport for parallel-roll convection in a rectangular container.

Heat-transport measurements are reported for thermal convection in a rectangular box of aspect ratio 10 x 5. Results are presented for Rayleigh numbers up to 35 R sub c, Prandtl numbers between 2 and 20, and wavenumbers between 0.6 and 1.0 K sub c, where R sub c and k sub c are the critical Rayleigh number and wavenumber for the onset of convection in a layer of infinite lateral extent. The measurements are in good agreement with a phenomenological model which combines the calculations of Nusselt number, as a function of Rayleigh number and roll wavenumber for two-dimensional convection in an infinite layer, with a nonlinear amplitude- equation model developed to account for sidewall attenuation. The appearance of bimodal convection increases the heat transport above that expected for simple parallel-roll convection.