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The aerodynamic design and performance analysis of two exhaust nozzles considered for use on a vehicle following an accelerating flight profile to a maximum flight speed corresponding to Mach 4.2 is presented. The vehicle operational requirements were set by the Air Vehicle Baseline Study commissioned by the Office of Naval Research. An afterburning engine cycle was assumed in the design and analysis process. The two nozzles investigated here were an axisymmetric convergent-divergent (C-D) nozzle with variable throat and exit area and an isentropic plug nozzle with variable throat area enabled by a translating outer cowl. Computational fluid dynamics was used to assist in the design process and to investigate the installed performance of the two nozzles at flight points from Mach 1.2 to Mach 4.2. For both nozzle configurations, the nozzles could not achieve perfectly expanded exit areas at the highest Mach numbers in order for the nozzle exit area to not exceed the vehicle cross sectional area. At the lower Mach numbers, the installed performance of the C-D nozzle was higher than that of the plug nozzle while at the highest Mach numbers, the performance of the two nozzles was similar. = nozzle exit radius corresponding to full expansion area y+ = wall normal coordinate θ = nozzle divergence angle Nomenclature

The ability of the WIND Navier-Stokes code to predict the physics of multi-species gases is investigated in support of future high-speed, hightemperature propulsion applications relevant to NASA's Space Transportation efforts. Three benchmark cases are investigated to evaluate the capability of the WIND chemistry model to accurately predict the aerodynamics of multi-species chemically non-reacting (frozen) gases. Case 1 represents turbulent mixing of sonic hydrogen and supersonic vitiated air. Case 2 consists of heated and unheated round supersonic jet exiting to ambient. Case 3 represents 2-D flow through a converging-diverging Mach 2 nozzle. For Case 1, the WIND results agree fairly well with experimental results and that significant mixing occurs downstream of the hydrogen injection point. For Case 2, the results show that the Wilke and Sutherland viscosity laws gave similar results, and the available SST turbulence model does not predict round supersonic nozzle flows accurately. For Case 3, results show that experimental, frozen, and 1-D gas results agree fairly well, and that frozen, homogeneous, multi-species gas calculations can be approximated by running in perfect gas mode while specifying the mixture gas constant and Ratio of Specific Heats.