The Quasi-Steady State Approximation (QSSA) can be an effective tool for reducing the size and stiffness of chemical mechanisms for implementation in computational reacting flow solvers. However, for many applications, stiffness remains, and the resulting model requires implicit methods for efficient time integration. In this paper, we outline an approach to formulating the QSSA reduction that is coupled with a strategy to generate C++ source code to evaluate the net species production rate, and the chemical Jacobian. The code-generation component employs a symbolic approach enabling a simple and effective strategy to analytically compute the chemical Jacobian. For computational tractability, the symbolic approach needs to be paired with common subexpression elimination which can negatively affect memory usage. Several solutions are outlined and successfully tested on a 3D multipulse ignition problem, thus allowing portable application across a chemical model sizes and GPU capabilities. The implementation of the proposed method is available at https://github.com/AMReX-Combustion/PelePhysics under an open-source license.

翻译：准稳态近似（QSSA）是一种有效工具，可用于缩减化学反应机理的规模与刚性，以便在计算反应流求解器中实施。然而，对于许多应用场景，刚性依然存在，所得模型仍需采用隐式方法以实现高效的时间积分。本文阐述了一种构建QSSA约简模型的方法，该方法结合了生成C++源代码的策略，以计算净物种生成速率与化学雅可比矩阵。代码生成组件采用符号化方法，为解析计算化学雅可比矩阵提供了一种简洁有效的策略。为确保计算可处理性，该符号化方法需与公共子表达式消除技术结合使用，但这可能对内存使用产生负面影响。本文概述了若干解决方案，并在一三维多脉冲点火问题上成功进行了测试，从而实现了跨不同化学模型规模与GPU计算能力的可移植应用。所提方法的实现已在开源许可下发布于 https://github.com/AMReX-Combustion/PelePhysics。