Abstract
A transient process to develop Bénard-Marangoni convection in a cavity with a free surface under horizontal thermal gradient is observed by a thermal camera. Tracer particles and laser light illumination are introduced to visualize the flow structures at surface and in the cavity at any section concerned. In the experiment of water, we confirm sensitiveness of the flow structures to the degradation of surface by a contamination of impurity. Convection flow velocity is highly affected by the contamination. A local Marangoni number is introduced to explain the sensitiveness of the flow structures and development to turbulent 3D convection. Existence of a region having negative local Marangoni number may characterize the transition from 2D flow to developed 3D convection.
