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 Fluids:
Copyright 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.  The following article appeared in 
Louis Leblanc, Maha Manoubi, Kadeem Dennis, Zhe (Rita) Liang, and Matei I. Radulescu, 
Phys. Fluids 25, 091106 (2013) and may be found at
http://dx.doi.org/10.1063/1.4820018
Louis, Maha and Kadeem as work
 

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