Oscillatory Rayleigh-Marangoni convection in a layer heated from above: Numerical simulations with an undeformable free surface

Joint action of buoyancy and thermocapillary forces can destabilize the motionless state in a liquid layer heated from above due to the coupling of internal and surface waves. The nonlinear evolution of this oscillatory instability is studied using three-dimensional direct numerical simulations with a pseudospectral Fourier-Chebyshev code. Alternating rolls and standing, oscillating squares are observed as final convective patterns The flow is strongly localized near the free surface. Buoyancy plays a negligible role in kinetic energy production.