非平衡流模拟参数ρ∞L有效性的数值分析

NUMERICAL ANALYSIS OF THE VALIDITY OF BINARY SCALING PARAMETERρ∞L IN NONEQUILIBRIUM FLOW

在非平衡流相似律现有研究成果的基础上,通过对化学反应特征时间、具体流场区域热化学状态、辐射输运方程的分析,并结合若干典型算例,讨论双体碰撞反应的非平衡尺度效应模拟参数ρ_∞L对高空高超声速飞行器全流场适用的条件.结果表明,当模拟参数ρ_∞L值低于一定范围时,在高超声速流场非平衡区中离解非平衡起主导作用,此时模拟参数ρ_∞L不仅对全流场的无量纲参数分布有效,而且对流场电离特性、模型气动热特性、分子光谱范围的驻点辐射谱强度都是有效的.模拟参数ρ_∞L的有效性与自由流速度、不同类物理量和流场不同区域均相关:当自由流速度增加时,对全场有效的ρ_∞L要求ρ_∞L值减小;与无量纲压力、密度和温度相比,对化学组元特别是离子组元分布有效的ρ_∞L所要求的ρ_∞L值更小;与模型头部区相比,在身部区有效的ρ_∞L所要求的ρ_∞L值更小.

In the present study, the validity of binary scaling parameter ρ∞L in nonequilibrium flow is numerically investigated with the charactristic time of chemical reactions similarity, thermochemical state of the flowfield, radiation transfer equation and similarity law for hypersonic flowfield. The numerical results show that the nonequilibrium dissociation process is dominant in the noqequilibrium region of the fiowfield when the parameter of ρ∞L is below its critical value. Therefore, it is validated that the parameter of ρ∞L can be applied in the simulation of the nondimensional variable distributions, wall heat transfer and ionization properties in the whole flow field, and molecular radiation intensity at the stagnation point. In addition, the effects of free stream velocities, the corresponding variables and flow regions on the validity of ρ∞L are also discussed.