N2, O2, NO state-to-state vibrational kinetics in hypersonic boundary layers: The problem of rescaling rate coefficients to uniform vibrational ladders

The NO formation in a hypersonic boundary layer is investigated by solving a numerical code that couples fluid dynamics and state-to-state vibrational kinetics. An N-2/N/O-2/O/NO mixture is considered to simulate the space vehicle Earth re-entry problem. Two new sets of state-to-state rate coefficients of the processes O + N-2(v) <-> NO(w) + N and N + O-2(v) <-> NO(w) + O are used, calculated in our research group by means of a molecular dynamics approach. Particular attention is payed to rescale the rates of different kinetic processes in order to have a unique vibrational scale for each molecular species (N-2, O-2, NO). This is not obvious because vibrational levels, obtained from asymptotics of three-body potential of different collisional systems, often do not match, particularly for high-lying vibrational states. The reactions involving NO affect the mass fractions, the molecular vibrational distributions and the heat flux in the boundary layer. (C) 2014 Elsevier B.V. All rights reserved.