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Center for Nonlinear Studies |
We study gravitational effects on reacting flows (premixed flames) using the Boussinesq buoyancy approximation. We consider fluids with low Prandtl and high Froude numbers (heat diffusion dominates over viscous dissipation, and reaction dominates over gravitational effects). These conditions result in a thin, laminar flame which separates reaction products from reactants. We consider two geometrical configurations: Rayleigh-Taylor unstable flames and rising flame bubbles. For the Rayleigh-Taylor system, we focus on the effective flame speed, on the the stability properties of the flame, and the effects of imposed symmetry. In the case of rising bubbles we show that, under particular conditions, all initially small bubbles follow the same growth pattern, regardless of flame speed, reaction type, gravity, viscosity, initial size, and, to some extent, initial shape of the bubble. We develop criteria under which the bubble follows the similarity solution and discuss the properties of the similarity solution.
Host: Misha Chertkov