Effects of vibrational nonequilibrium on axisymmetric hypersonic nozzle design

A vibrational nonequilibrium Navier-Stokes computational algorithm is used to determine the flow conditions in several existing nozzles. Vibration freezes near the throat for typical stagnation conditions in these nozzles. The freezing causes the gas to behave as though the ratio of specific heats is constant. It is shown that the thick boundary layers in hypersonic nozzles create problems in their design using classic techniques. As a result, existing nozzles such as the NASA Langley Mach 17 Nitrogen Tunnel may be underexpanded and operate with poor test section conditions. A design technique based on the Navier-Stokes equations including the effects of vibrational nonequilibrium are required for high quality flow.