Towards direct simulations of counterflow flames with consistent differential-algebraic boundary conditions

A new approach for the formulation of boundary conditions for the counterflow configuration is presented. Upon discretization of the steady-state Navier-Stokes equations at the inflow boundaries, numerically algebraic equations are imposed as boundary conditions, while upon discretization of the unsteady Navier-Stokes equations at the outflow, differential boundaries result. It is demonstrated that the resulting numerical differential-algebraic boundary conditions are suitable to account for the multi-directional character of the flow at the boundaries of the counterflow configuration