Fundamental Rayleigh-Benard type experimental and theoretical studies are performed to measure for the first time the effect of interfacial phenomena on the stability and structure of thermocapillary and buoyancy driven conection in low Prandtl number liquid metal and semiconductor fluids. The experiments will be carried out on liquid tin and lead heated from below and will utilize an ultrahigh vacuum system with an ion sputter gun and a unique Auger and ELS analysis capability for establishing and maintaining atomically clean surfaces at working temperatures for extended periods of time. The system allows for measuring monolayer concentration levels of surface active materials. Stability limits and surface morphology will be verified for low Prandtl number fluids experimentally for both the onset of convection and the nonlinear transition to oscillatory convection modes as a function of solute concentration, evaporation rates and aspect ratio. Theoretical studies designed to guide and interpret the experimental work will include two and three dimensional analyses of instability and bifurcation phenomena in fluid layers. The effect of interfacial phenomena, including surface concentraion, vapor recoil, surface adsorption and deflection will be studied in detail.
