Influence of buoyancy in unconfined flames
Using the soap bubble technique, we visualize the dynamics of unconfined hydrogen-air flames using high speed schlieren video - a technique that permits to see density gradients. For sufficiently weak mixtures, i.e., low flame speeds, buoyancy effects become important, as shown in the following two photographs. As the flame begins to grow inside the soap bubble, the light products of combustion inside the flame ball begin to rise, forming a mushroom-shaped flame. The critical dimension of flame balls that will begin to rise due to buoyant forces is given by equating the time scale for flame propagation to the time scale of convection by buoyant forces. More details can be found in our arXiv paper and video , which has won one of the three Van Dyke awards for the Gallery of Fluid Motion at the 65th Annual Meeting of the American Physical Society - Division of Fluid Dynamics . UPDATE 19-9-2013 : The article is now available in Physics of Fl...