Non-equilibrium air plasma chemistry in boundary layers

Numerical simulations of air plasmas have been performed within boundary layers near the surface of fast moving objects. A two-temperature model is used to cover both equilibrium and non- equilibrium conditions, which includes eleven species and twenty six forward and backward high-temperature chemical reactions of ionization, dissociation, and charge exchange [1]. The model is coupled to a conventional boundary-layer model [2] that enables to calculate the temperature and species distribution along the front stagnation line. At these plasma conditions (pressures of 0.001-0.1 atm and temperatures of 1000-10000 K) the plasma does not reach equilibrium due to short interaction times (<ms) and has to be treated as non-equilibrium plasma.

[1] B. Parent, Physics of Fluids 33, 046105 (2021)

[2] J. A. Fay and F. R. Riddell, J. Aeronautical Sci. 25, 73-121 (1958)