VIBRATIONALLY RELAXING FLOW OF N-2 PAST AN INFINITE CYLINDER

The results of a numerical study aimed to verify the accuracy of the t hermodynamic models based on the Boltzmann distribution in the hyperso nic regime and to detect discrepancies, if any, with the analysis base d on the more rigorous method of vibrational kinetics are presented an d discussed. The test case considered in the study is the steady, two- dimensional, chemically inert, inviscid flow of diatomic nitrogen past an infinite cylinder in a uniform stream at M(x) = 6.5. The vibration al relaxation has been calculated from the standard vibrational energy rate equation, assuming a harmonic-oscillator behavior of N-2, and fr om a set of vibrational master equations that account for the first 10 vibrational energy levels of the N-2 molecule, assumed as an anharmon ic oscillator. The now patterns produced by the two calculation method s are thoroughly discussed and the critical: influence of the vibratio nal relaxation time, associated with the harmonic-oscillator models, i n determining agreement or disagreement with the results from the vibr ational kinetics method is evidenced.