LBL - 3855 1 7 - UC - 405 ERNEST ORLAND LAWRENCE BERKELEY NATIO AL LABORATORY An Adaptive Projection Method for the Modeling of Unsteady , Low - Mach Number Combustion

In this paper we present an adaptive projection method for modeling unsteady, lowMach reacting flow in an unconfined region. The equations we solve are based on a model for low-Mach number combustion that consists of the evolution equations for density, species concentrations, enthalpy, and momentum 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 timevarying, hierarchical grid structure composed of uniform rectangular grids of varying resolution. The integration scheme on the grid hierarchy is a recursive procedure in which a coarse grid is advanced, fine grids are advanced multiple steps to reach the same time as the coarse grid, and the coarse and the fine grids are synchronized. The method is valid for multiple grids on each level and multiple levels of refinement. The method is currently implemented for laminar, axisymmetric flames with a reduced kinetics mechanism and a Lewis number of unity. Two methaneair flames, one steady and the other flickering, are presented as numerical examples.