Flow Transition in a Free Rectangular Liquid Film Under a Temperature Gradient
Ichiro Ueno and Toshiki Watanabe
Thermocapillary-driven flow in a free rectangular liquid film under a temperature gradient parallel to the free surfaces is examined with experimental approaches. Silicone oil of 5 cSt is employed as an examined fluid. Under a small temperature difference, a two-dimensional basic flow appears; the basic flow is double-layered, that is, the fluid flows from a hot wall to a cool wall on free surfaces and returns in the interior region of the film. The flow exhibits a transition to an ‘internal’ oscillatory flow, that is, a three-dimensional flow emerges inside the film in addition to the double-layered basic flow. The authors found out that the flow exhibits a significantly different bifurcation in the case of thinner liquid film. The basic flow itself turns to a single-layered, span-wise cellular flow. The authors will introduce such unique bifurcations in the thin free liquid film and their occurring condition.
Keywords: Thermocapillary-driven flow, free liquid film, flow patterns, hydrothermal wave instability, double-layered flow, single-layered flow.