THERMOCAPILLARY HOW WITH EVAPORATION AND CONDENSATION AT LOW GRAVITY .2. DEFORMABLE SURFACE

The free surface behaviour of a volatile wetting liquid at low gravity is studied using scaling and numerical techniques. An open cavity mod el, which was applied in part 1 to investigate fluid flow and heat tra nsfer in non-deforming pores, is used to evaluate the influence of con vection on surface morphology with length scales and subcooling/superh eating limits of 1 less than or equal to D less than or equal to 10(2) mu m and similar to 1 K, respectively. Results show that the menisci shapes of highly wetting fluids are sensitive to thermocapillary flow and to a lesser extent the recoil force associated with evaporation an d condensation. With subcooling, thermocapillarity produces a suction about the pore centreline that promotes loss of mechanical equilibrium , while condensation exerts an opposing force that under some conditio ns offsets this destabilizing influence. With-superheating, thermocapi llarity and evaporation act in the same direction and mutually foster; surface stability. All of these trends are magnified by high capillar y and Riot numbers, and the stronger circulation intensities associate d with small contact angles. These phenomena strongly depend on the th ermal and interfacial equilibrium between the liquid and vapour, and h ave important ramifications for systems designed to maintain a pressur e differential across a porous surface.