Behaviour of drops in contact with liquid surfaces at non wetting conditions

The behaviour of small liquid drops, hanging from a circular disk and approaching a pool surface of a liquid at different temperatures, is studied experimentally and numerically. The experiments show that if isothermal conditions prevail the drop is immediately engulfed by the liquid. On the contrary, if the temperature of the drop is sufficiently larger or sufficiently smaller than the temperature of the liquid surface, this engulfment is prevented even if the drop is pressed on the liquid surface and "enters" the liquid pool. A number of experiments have been carried out on silicone oils (with different viscosities). At the same time the problem was studied numerically with the assumption that a thin air film is formed between the drop and the liquid bath surface, by the entrainment of the surrounding air caused by the Marangoni flow, and the pressure in the air film balances the pressure necessary to keep the drop submerged in the liquid bath.