On the Determination of General Resolution Requirements of Direct Numerical Simulations using Detailed Chemistry

Abstract

Numerical simulations of reacting flows often rely on direct integration of the continuity and momentum equations while transporting each chemical species and integrating their source term. However, requirements on the grid size and time step to resolve all the relevant physics is not generally well defined. In practice, information regarding convergence is gathered from the corresponding non-reacting flow, one-dimensional laminar flame, and full convergence studies. The establishment of general criteria or benchmarks relating convergence of these three aspects would decrease research and computational effort performing detailed convergence studies and increase consistency in the literature. To support this goal, studies were performed relating the convergence of the global flow field of a laminar reacting flow to the convergence, in space and time, of the corresponding one-dimensional flame and non-reacting flow. It was found that grid convergence of the global flow field was related to, but had more stringent requirements than either of the two separate cases while the required time step was the same. These results contribute to the development of satisfactory general criteria and benchmarks for determining convergence across specific flow cases, chemical mechanisms, and numerical implementations.

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