Numerical solutions of scramjet nozzle flows

The accurate prediction of nozzle flows for ramjets and scramjets is important for design and system performance analysis. The problem is made complex by the presence of strongly nonuniform entrance profiles, especially for scramjets (which have no throat at the end of the combustor). Thus, turbulent mixing and, often, chemical reactions can be expected to be under way during the expansion process. The rapid expansion common in nozzles implies substantial radial pressure gradients. Taken together, these requirements lead to the necessity of utilizing the full Navier-Stokes equations for a compressible, multicomponent, turbulent flow with finite-rate chemistry. For this work, the unsplit, explicit, MacCprmack unsteady/finite-difference method was used to solve the equations of motion. Turbulence transport is represented with a turbulent kinetic energy model. Chemistry is treated at this time by either frozen equilibrium or a simple, global finite-rate model. Calculations are presented for a typical scramjet case where the effects of nonuniform inflow profiles on the nozzle flowfield and performance are shown for different nozzle designs.