STEADY AND OSCILLATORY BIMODAL CONVECTION

Steady three-dimensional convection in the form of bimodal cells in a fluid layer heated from below with rigid boundaries studied through numerical computations for Prandtl numbers in the range 10 less than or similar to P less than or similar to 100. The stability of the steady solutions with respect to disturbances of various symmetries has been analysed. Typically, the range of stable steady bimodal convection is restricted by the transition to oscillatory bimodal convection. The oscillations preserve the spatial symmetry of the steady bimodal convection pattern in the case of high P and higher wavenumbers, but break it in the case of lower P or lower wavenumbers in the range that has been investigated. Some comparisons are made with experimental observations. The transition from bimodal to knot convection has also been studied.