...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Combustion and Flame >A second-order dynamic adaptive hybrid scheme for time-integration of stiff chemistry
【24h】

A second-order dynamic adaptive hybrid scheme for time-integration of stiff chemistry

机译：一种二阶动态自适应杂交方案，用于僵硬化学的跨越化学

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A dynamic adaptive hybrid integration (AHI) scheme of second-order accuracy (AHI2) is proposed for time-integration of chemically reacting flows involving stiff chemistry. AHI2 is extended from a first-order AHI method (AHI1) developed in a previous study, which showed that when significant radical sources are present in the non-chemical source terms, splitting the chemical and the transport sub-systems may incur O (1) errors unless the splitting time steps are comparable to or smaller than that required for explicit integration. As such, the transport term needs to be carried during the integration of stiff chemistry to avoid the large splitting errors. In AHI, fast species and reactions that may induce stiffness are treated implicitly, while the non-stiff variables and source terms, including slow reactions and the mixing term, are treated explicitly. The separation of fast-slow chemistry is performed on-the-fly based on analytically evaluated timescales for species and reactions, such that the complexity of the implicit core in the governing equations is minimized at each time step and the time-integration can be performed with high efficiency. The newly developed AHI2 scheme combines the midpoint scheme and the trapezoidal rule to achieve second-order accuracy. The second-order scheme is tested with a toy problem, as well as auto-ignition and unsteady perfectly stirred reactors (PSR) with detailed chemistry. Results show that AHI2 can significantly improve accuracy compared with AHI1. It was further found that AHI2 can accurately predict extinction of unsteady PSRs while the Strang splitting scheme fails to control the error, showing the necessity not to split the chemistry and transport source terms for prediction of extinction or forced-ignition problems involving significant radical sources. Further analysis of numerical efficiency shows that for auto-ignition AHI2 reduces computational cost primarily through the reduction in the number of variables to be solved implicitly, and the time-saving increases with the mechanism size, reaching approximately 70% for the 111-species USC-Mech II compared with a fully implicit scheme. For unsteady PSR involving homogeneous mixing, AHI2 achieved speedup factors of 20 to 30 compared with the Strang splitting scheme. Furthermore, sparse matrix techniques are integrated into AHI2 (AHI2S) to achieve high computational efficiency. It is shown that the computational cost of AHI2-S is overall linearly proportional to the mechanism size and is comparable to that of evaluating reaction rates using CHEMKIN-II subroutines. It is further shown that AHI2-S achieves a speed-up factor of around two compared with the efficient fully implicit sparse solver LSODES with analytic Jacobian.(c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：提出了二阶精度（AHI2）的动态自适应混合集成（AHI）方案用于涉及难以化学的化学反应流动的时间集成。 AHI2从先前研究中开发的一阶AHI方法（AHI1）扩展，这表明当非化学源术语中存在显着的根治源时，分裂化学物料和运输子系统可能会产生o（1 ）误差，除非分割时间步骤可与明确集成所需的比较或小。因此，需要在刚性化学的集成过程中携带运输术语以避免大的分裂误差。在AHI中，明确地治疗可能诱导刚度的快速物种和反应，而非硬变量和源术语，包括缓慢反应和混合项。基于用于物种和反应的分析评估的时间尺度，在飞行中进行快速慢化学的分离，使得在每个时间步骤中，在控制方程中的隐式芯的复杂性最小化，并且可以执行时间集成效率高。新开发的AHI2方案结合了中点方案和梯形规则来实现二阶精度。用玩具问题测试二阶方案，以及具有详细化学性的自动点火和非定常搅拌反应器（PSR）。结果表明，与AHI1相比，AHI2可以显着提高精度。进一步发现，AHI2可以准确地预测不稳定的PSR，而斯特朗分裂方案无法控制误差，则表明必须不将化学和运输源术语分开以预测涉及显着的自由基来源的消光或强制点火问题。进一步分析数值效率的进一步分析表明，对于自动点火AHI2，AHI2主要通过暗示待解决的变量数量的减少来减少计算成本，并节省了机制尺寸，对于111种USC达到大约70％ -mech II与完全隐含的方案相比。对于涉及均匀混合的不稳定PSR，与斯特朗施联方案相比，AHI2实现了20至30的加速因子。此外，稀疏矩阵技术集成到AHI2（AHI2S）中以实现高计算效率。结果表明，AHI2-S的计算成本与机构尺寸总体线性成比例，并且与使用Chemin-II子程序评估反应速率的计算成本。进一步示出了与具有分析雅加诺的有效完全隐含的稀疏求解器Lsodes相比，AHI2-S与分析雅比亚的有效完全隐含的稀疏求解器Lsodes相比实现了大约两个。（c）2021燃烧研究所。由elsevier Inc.保留所有权利发布。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号