详细化学反应动力学动态自适应加速

A Dynamic Adaptive Acceleration Method of Detailed Chemistry

详细化学反应机理应用于三维、高度瞬态的湍流燃烧数值模拟时,计算成本巨大.为此,本文提出了一种基于动态自适应建表(ISAT)和动态自适应化学(DAC)的化学反应动力学动态自适应加速方法.该方法基于组分空间的低维流形特性,采用主成分分析法将燃烧区域中的网格节点(或颗粒)从组分空间向低维空间内投影,根据投影点在低维空间内的概率密度函数来刻画系统的非均匀性,进而自适应地选择ISAT和DAC进行加速.本文通过设置内燃机模拟算例,使用甲烷GRI Mech3.0机理,初步验证了新方法的性能。计算结果表明,在保证计算精度的同时,新方法具有明显的加速优势。对于包含500个颗粒的内燃机模拟算例,加速因子可以达到使用ISAT的2.7倍、DAC的1.7倍、固定ISAT-DAC联合的1.8倍。

The incorporation of detailed chemistry into the turbulent combustion simulation is challenging particularly for multi-dimensional, highly transient combustion process. In this study,a dynamic adaptive approach combing the in situ adaptive tabulation（ISAT） and the dynamic adaptive chemistry（DAC） is proposed to accelerate chemistry calculations. In this method, principle component analysis is first employed to identify a low-dimensional subspace in the composition space, in which the composition inhomogeneity of the computational cells is then quantified through reconstructing the probability density function（PDF） of composition. ISAT and DAC is dynamically determined for different regions of the composition space based on the reconstructed PDF. The proposed approach is preliminarily validated in IC engine model simulations with the GRI Mech3.0 of methane/air mixture and the performance is analyzed. For the testing cases considered, the dynamic adaptive approach is 2.7 times, 1.7 times and 1.8 times faster than the standalone ISAT and DAC and the fixed combined ISAT-DAC approach for chemistry calculations respectively, while achieving almost the same level of accuracy.