Experimental Phenomena and Exploratory Theoretical Driving Mechanisms for Directional Flows Occurring in λ-Type Heated/Cooled thin Liquid Wedges Confined Between Fluidic Interfaces

Abstract

The work reports some new experimental and theoretical results regarding the abnormal behaviors of liquid flows taking place in a thin liquid wedge situated under an as symmetric temperature gradient. These experimental results, obtained using particle image velocimetry (PIV) technique, are additional to those having been reported previously by the same research group. More specifically, a tangential directional flow can be induced when a sufficiently thin liquid wedge confined in two fluidic interfaces is heated or cooled at a point. The flows caused by point heating are in direction toward the thinner region of the liquid wedge whereas those caused by point cooling flow in the opposite direction, toward the thicker region. In theory, these flows are here interpreted as driven by thermodynamic mechanisms rather than by usual thermo-capillary effects. Theoretical results show that the presence of the flow is necessary for such a point-heated/cooled liquid wedge to evolve toward the minimum of interfacial energy. Under the free-force boundary conditions, the flow velocity predicted in theory is in good agreement with the experimental data in direction, scale of order, and variation behaviors with changing experimental conditions.