Bubble-induced Marangoni convection

Abstract

Thermal Marangoni convection about a 1mm radius air bubble situated under a heated wall of constant temperature immersed in a silicone oil layer (Pr = 220) of constant depth 5mm was experimentally investigated using a flow imaging technique known as particle image velocimetry, or PIV. The response to increasing temperature gradient and Marangoni numbers in the range 145≤Ma≤363 was investigated. For all experiments, steady-state convection was observed and primary, thermocapillary- driven vortices were seen to develop on both sides of the bubble, along with a jet-like flow of liquid from the bubble tip that protruded into the bulk liquid below it. Beneath these primary flow structures, secondary, slower-moving vortices were also observed, and these buoyancy-driven vortices rotated in opposite direction to the primaries.