Preconditioned Navier-Stokes Solution Technique for Laminar Methane-Air Non-Premixed Combustion

A solution-adaptive Navier-Stokes technique is presented which incorporates a fully implicit solution algorithm with low Mach number preconditioning. The equations are formulated for generalized n-species/rareactions Arrhenius chemistry and are cast in a generalized coordinate frame for application to arbitrary geometries. The grid adaption strategy employs a line-by-line equi-distribution concept in which grid points are re-distributed along each coordinate line during the course of the solution process according to gradients of user specified dependent variables. The solution technique is demonstrated on a laminar methane-air diffusion flame using a 17-species/58-reaction chemistry mechanism. Computed results for temperature, mole fraction, and velocity compare favorably with experimental results. Typical computations require a few hours CPU time on a standard desktop engineering workstation. The accuracy of the computed results illustrate that the solution strategy presented in this paper is an attractive means of computing reacting flows with detailed chemistry.