Pattern dynamics of the Bénard-Marangoni instability in a medium aspect ratio container.

This study is an experimental work devoted to Benard-Marangoni instability in a medium vessel. The free surface deformation is visualised by interferometry and the free surface temperature field by infrared thermography. These two techniques are complementary, since each method provides specific information, which may allow the detection of peculiar phenomena such as the spatial resonance, which is a situation in which the interfacial deformation does not conform to the flow pattern. The influences of the aspect ratio, Rayleigh, Biot and Prandtl numbers, are considered. More dynamics are induced by increasing the Biot number. Conversely, increasing the Prandtl number reduces the dynamics. The deformation magnitude and the wavenumber increase as functions of the gradient of temperature. Two behaviours of the deformation, as a function of Prandtl and Biot numbers, were observed, depending on the value of the applied gradient of temperature. The obtained results are discussed with previous experimental, theoretical and numerical studies. Results of other authors were confirmed concerning the evolution as functions of the gradient of temperature and the aspect ratio and new results were obtained concerning the behaviour of the pattern as functions of Pr and Biot numbers.