Modeling low mach number reacting flow with detailed chemistry and transport |
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Authors: | H N Najm O M Knio |
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Affiliation: | (1) Sandia National Laboratories, Livermore, CA, USA;(2) The Johns Hopkins University, Baltimore, MD, USA |
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Abstract: | An efficient projection scheme is developed for the simulation of reacting flow with detailed kinetics and transport. The
scheme is based on a zero-Mach-number formulation of the compressible conservation equations for an ideal gas mixture. It
relies on Strang splitting of the discrete evolution equations, where diffusion is integrated in two half steps that are symmetrically
distributed around a single stiff step for the reaction source terms. The diffusive half-step is integrated using an explicit
single-step, multistage, Runge-Kutta-Chebyshev (RKC) method. The resulting construction is second-order convergent, and has
superior efficiency due to the extended real-stability region of the RKC scheme. Two additional efficiency-enhancements are
also explored, based on an extrapolation procedure for the transport coefficients and on the use of approximate Jacobian data
evaluated on a coarse mesh. We demonstrate the construction in 1D and 2D flames, and examine consequences of splitting errors.
By including the above enhancements, performance tests using 2D computations with a detailed C1C2 methane-air mechanism and a mixture-averaged transport model indicate that speedup factors of about 15 are achieved over
the starting split-stiff scheme. |
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Keywords: | Reacting flow time integration operator splitting Runge-Kutta-Chebyschev stiffness |
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