A fitting formula for radiative cooling based on non-local thermodynamic equilibrium population from weakly-ionized air plasma

24th IUPAP Conference on Computational Physics

物理学;计算机科学

Ogino, Yousuke^1 ; Nagano, Atsushi^1 ; Ishihara, Tomoaki^1 ; Ohnishi, Naofumi^1

Department of Aerospace Engineering, Tohoku University, 6-6-01 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-8579, Japan^1

关键词: Atomic and molecular process;    Blast wave propagation;    Elementary process;    Local thermodynamic equilibrium;    Optically thin plasmas;    Population numbers;    Radiative cooling;    Temperature range;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/454/1/012080/pdf
DOI  :  10.1088/1742-6596/454/1/012080

学科分类：计算机科学（综合）

来源: IOP

【 摘 要 】

A fitting formula for radiative cooling with collisional-radiative population for air plasma flowfield has been developed. Population number densities are calculated from rate equations in order to evaluate the effects of nonequilibrium atomic and molecular processes. Many elementary processes are integrated to be applied to optically-thin plasmas in the number density range of 1012/cm3≤ N ≤ 1019/cm3and the temperature range of 300 K ≤ T ≤ 40,000 K. Our results of the total radiative emissivity calculated from the collisional-radiative population are fitted in terms of temperature and total number density. To validate the analytic fitting formula, numerical simulation of a laser-induced blast wave propagation with the nonequilibrium radiative cooling is conducted and successfully reproduces the shock and plasma wave front time history observed by experiments. In addition, from the comparison between numerical simulations with the radiation cooling effect based on the fitting formula and those with a gray gas radiation model that assumes local thermodynamic equilibrium, we find that the displacement of the plasma front is slightly different due to the deviation of population probabilities. By using the fitting formula, we can easily and more accurately evaluate the radiative cooling effect without solving detailed collisional-radiative rate equations.