PATTERN SELECTION IN BENARD-MARANGONI CONVECTION

Pattern formation in fluids with a free flat upper surface is examined. On that surface, the Marangoni effect provides an additional instability mechanism. Based on amplitude equations it is shown that phase instabilities confine the region of stable hexagons to a narrow band of wavelengths. On the other hand we developed a numerical scheme that allows for a direct integration of the fully three-dimensional hydrodynamic equations. There we show the evolution of random patterns and the creation and stabilization of defects as well as the instability of hexagonal patterns lying outside the stable band of wave vectors.