Improved boundary conditions for the DNS of reacting subsonic flows

In this paper, we develop a method of prescribing time dependent boundary conditions for reacting flows. The method builds on earlier results, and derives from a linearization of the flow field around a base state. The base state is specified in terms of the flow dilatation, and we establish a general expression for the dilatation in reacting flows at low Mach number. This expression is then used to derive acoustically transparent boundary conditions. The utility of the approach is demonstrated via a number of laminar flame calculations, ranging in complexity from single step chemistry to a multi-step methane mechanism. The accuracy of the resulting solutions is found to be superior to those obtained using other means. © 2010 Springer Science+Business Media B.V.