Numerical simulation of nonequilibrium flow in high-enthalpy shock tunnel

摘要

The flow field of a nozzle starting process with thermal and chemical nonequilibrium has been simu- lated. This flow is produced in high enthalpy impulse facilities such as the free piston shock tunnel. The governing equations are the axisymmetric, compressible Navier-Stokes equations. In this study, Park's two-temperature model, where air consists of five species, is used for defining the thermodynamic proper-ties of air as a driven gas. The numerical scheme employed here is the hybrid scheme of the explicit and implicit methods, which was developed in our laboratory, along with AUSM~+ to evaluate inviscid fluxes. In the present simulation, the Mach number of an incident shock wave is set at M_s = 10.0. It corresponds to a specific enthalpy, h_0, of 12 MJ/kg. The results clearly show the complicated thermal and chemical nonequilibrium flow field around the end of the shock tube section and at the nozzle inlet dur-ing the initial stage of the nozzle starting process. They also suggest that the phenomenon of nozzle melting might be associated with a flow separation at the nozzle inlet.