Munafò A, Panesi M, Magin T E
Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-Saint-Genèse, Belgium.
Department of Aerospace Engineering, Talbot Laboratory, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, Illinois 61801, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Feb;89(2):023001. doi: 10.1103/PhysRevE.89.023001. Epub 2014 Feb 5.
A Boltzmann rovibrational collisional coarse-grained model is proposed to reduce a detailed kinetic mechanism database developed at NASA Ames Research Center for internal energy transfer and dissociation in N(2)-N interactions. The coarse-grained model is constructed by lumping the rovibrational energy levels of the N(2) molecule into energy bins. The population of the levels within each bin is assumed to follow a Boltzmann distribution at the local translational temperature. Excitation and dissociation rate coefficients for the energy bins are obtained by averaging the elementary rate coefficients. The energy bins are treated as separate species, thus allowing for non-Boltzmann distributions of their populations. The proposed coarse-grained model is applied to the study of nonequilibrium flows behind normal shock waves and within converging-diverging nozzles. In both cases, the flow is assumed inviscid and steady. Computational results are compared with those obtained by direct solution of the master equation for the rovibrational collisional model and a more conventional multitemperature model. It is found that the proposed coarse-grained model is able to accurately resolve the nonequilibrium dynamics of internal energy excitation and dissociation-recombination processes with only 20 energy bins. Furthermore, the proposed coarse-grained model provides a superior description of the nonequilibrium phenomena occurring in shock heated and nozzle flows when compared with the conventional multitemperature models.
提出了一种玻尔兹曼振转碰撞粗粒化模型，以简化美国国家航空航天局艾姆斯研究中心开发的用于描述N(2)-N相互作用中内能转移和解离的详细动力学机制数据库。该粗粒化模型通过将N(2)分子的振转能级归并到能量区间来构建。假设每个区间内能级的粒子数在局部平动温度下遵循玻尔兹曼分布。通过对基本速率系数求平均得到能量区间的激发和解离速率系数。将能量区间视为独立的物种，从而允许其粒子数具有非玻尔兹曼分布。将所提出的粗粒化模型应用于研究正激波后和缩放喷管内的非平衡流动。在这两种情况下，均假设流动无粘且稳定。将计算结果与通过直接求解振转碰撞模型的主方程以及更传统的多温度模型所得到的结果进行了比较。结果发现，所提出的粗粒化模型仅用20个能量区间就能准确解析内能激发和解离-复合过程的非平衡动力学。此外，与传统的多温度模型相比，所提出的粗粒化模型能更好地描述激波加热和喷管流动中出现的非平衡现象。
