Hypervelocity flow of dissociating nitrogen downstream of a blunt nose

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Abstract
The nature of the non-equilibrium flow of strongly dissociating nitrogen has been investigated by a series of simulation calculations using non-equilibrium (finite rate) chemical reactions. These were made with the equilibrium flux method (EFM), and the results have been found to compare favourably with experimental results obtained with a free-piston driven shock-tube wind tunnel which was used to obtain interferograms of the flow of pure nitrogen over a blunt-nosed body, 65 mm long at three angles of incidence. No simple relation between the flow with non-equilibrium chemistry and those for frozen or equilibrium chemistry has been found. The problems of relating test flows produced in the shock tunnel to flight conditions are investigated by considering the test flows that might be produced by some ‘ideal equivalent wind tunnels’. It is shown that the degree of frozen dissociation in the test flow in a shock tunnel is not a serious matter, but that the large difference in Mach number between shock tunnel flows and flight conditions may be more important.