The effect of two-dimensionality on the suppression of thermal turbulence

Abstract

Two-dimensional thermal convection of air between horizontal plates of length much greater than their separation distance is studied numerically by solution constraining motions to lie in a single vertical plane. Rayleigh numbers from 105 to 107 are employed. Steady rolls with wavelength twice the plate-separation were obtained in both cases. As the experimental two-dimensional constraint is relaxed, short-period turbulent fluctuations in temperature develop, the rolls or cells become only quasi-steady, and their wavelength increases. For the three-dimensional case, very large width-to-height ratios and averaging periods are found necessary before the temperature variance in time approaches the variance in the horizontal.