An Adaptive Projection Method for Unsteady, Low-Mach Number Combustion

We present an adaptive projection method for modeling unsteady, low-Mach reacting flow in an unconfined region. The equations are based on a model for low-Mach number combustion that consists of evolution equations coupled with a constraint on the divergence of the flow. The algorithm is based on a projection methodology in which we first advance the evolution equations and then solve an elliptic equation to enforce the divergence constraint. The adaptive mesh refinement (AMR) scheme uses a time-varying hierarchy of rectangular grids. The integration scheme is a recursive procedure in which coarse grids are advanced, fine grids are advanced to the same time as the coarse grids, and the coarse and fine grid data are then synchronized. The method is currently implemented for laminar, axisymmetric flames with a reduced kinetics mechanism and a Lewis number of unity. Three methane-air flames, two steady and one flickering, are presented as numerical examples.