A second-order dynamic adaptive hybrid scheme for time-integration of stiff chemistry
نویسندگان
چکیده
A dynamic adaptive hybrid integration (AHI) scheme of second-order accuracy (AHI2) is proposed for time-integration chemically reacting flows involving stiff chemistry. AHI2 extended from a first-order AHI method (AHI1) developed in previous study, which showed that when significant radical sources are present the non-chemical source terms, splitting chemical and transport sub-systems may incur O(1) errors unless time steps comparable to or smaller than required explicit integration. As such, term needs be carried during chemistry avoid large errors. In AHI, fast species reactions induce stiffness treated implicitly, while non-stiff variables including slow mixing term, explicitly. The separation fast-slow performed on-the-fly based on analytically evaluated timescales reactions, such complexity implicit core governing equations minimized at each step can with high efficiency. newly combines midpoint trapezoidal rule achieve accuracy. tested toy problem, as well auto-ignition unsteady perfectly stirred reactors (PSR) detailed Results show significantly improve compared AHI1. It was further found accurately predict extinction PSRs Strang fails control error, showing necessity not split terms prediction forced-ignition problems sources. Further analysis numerical efficiency shows reduces computational cost primarily through reduction number solved time-saving increases mechanism size, reaching approximately 70% 111-species USC-Mech II fully scheme. For PSR homogeneous mixing, achieved speedup factors 20 30 Furthermore, sparse matrix techniques integrated into (AHI2-S) shown AHI2-S overall linearly proportional size evaluating reaction rates using CHEMKIN-II subroutines. achieves speed-up factor around two efficient solver LSODES analytic Jacobian.
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ژورنال
عنوان ژورنال: Combustion and Flame
سال: 2021
ISSN: ['1556-2921', '0010-2180']
DOI: https://doi.org/10.1016/j.combustflame.2021.01.045