Remarks on the Design of Hypersonic High Reynolds Number Nozzles with Energy Addition

Abstract

This paper addresses issues that must be considered relative to the design of hypersonic wind tunnel nozzles where energy is added to the core flow in the nozzle to achieve true temperature simulation conditions at flight conditions up to Mach 12 in the air-breathing propulsion flight corridor. The paper draws on research experience relative to the Radiantly Driven Hypersonic Wind Tunnel (RDHWT), which was sponsored by the Arnold Engineering Development Center (AEDC), Arnold Air Force Base, Tennessee. The Air Force objectives were to develop technologies that would permit the development of a truetemperature Mach 8 to 12 aero propulsion test capability for development testing of future hypersonic air-breathing propulsion weapons systems. Numerous technology tools are needed to design nozzles for a radiantly driven hypersonic wind tunnel. Generally, it is believed that one of these tools should be a nozzle design code based on the Navier-Stokes equations that can calculate a heated primary core of air and secondary annular cooler flow of nitrogen. The Reynolds numbers of the flow range up to 10 10 , which is much higher than generally experienced in hypersonic nozzle flows. The boundary and mixing layers of the flow are undoubtedly turbulent and thus require an appropriate turbulence model(s) for the boundary-layer and mixing-layer calculations. Under the RDHWT, research program data from three sets of experiments were utilized to test turbulence models and codes. Two sets of experiments were conducted by Princeton University. AEDC examined results from existing experimental data from the AEDC White Oak Hypervelocity Wind Tunnel 9 Facility. All experiments were conducted at Reynolds numbers up to about 10 8 . Surprisingly, no Reynolds number effects (i.e., boundary-layer growth) were observed in the Princeton experiments even with an order-of-magnitude change in Reynolds number. The physical scale of the experiment was very small and possibly contributed to the lack of observation of any Reynolds number effects. Because no Reynolds number effects were observed, it was decided to evaluate experimental data available from the AEDC Tunnel 9 Mach 14 nozzle, whose scale is about the same as would be used in a medium-scale, radiantly driven hypersonic wind tunnel. Reynolds number effects were observed in the nozzle as expected.