THE STABILITY OF FREE-CONVECTION IN A PARTICLE-FLUID MIXTURE WITH A FREE-SURFACE

The onset of thermal instability for simultaneous surface tension and buoyancy driven mechanisms in a horizontal fluid layer with suspended particles is theoretically investigated by means of a small disturbanc e analysis. The critical Marangoni, Rayleigh and wave numbers are comp uted and compared with those known for a pure fluid. The effect of the particles enters through three parameters: gamma, phi and Gamma. The first describes how much particles are present, the second is determin ed by the particle-fluid thermal energy change ratio (named the heat l oading ratio) and the third characterizes the size of the individual p articles (the particle aspect ratio). It is found that when gamma or p hi increases the system is destabilized while the raise of Gamma desta bilizes or stabilizes the layer depending on whether the Rayleigh numb er is positive or negative.