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Results of a numerical simulation of the unsteady axisymmetric flow forming in joint process of starting an impulse wind tunnel equipped with a plenum chamber and a throttling device as well as starting an axisymmetric inlet tested in this tunnel are reported. An impulse wind tunnel schematizing the hot-shot wind tunnel IT-302M based at ITAM and an operating flow regime of Mach number M = 8 obtained with a contoured nozzle were under consideration. There was applied a Reynolds-averaged Navier–Stokes code including the k-ω SST turbulence model. The starting process was initiated in accordance with the Riemann problem. The computed data showed a complicated starting shock-wave system forming in the nozzle and in front of the tested inlet, it included the primary shock wave, contact discontinuity transforming into a contact layer, inverse shock wave, expansion wave. This system determined the lasting of the processes of starting the nozzle and the inlet proper. As it was identified, a chain of changing inlet flow modes occurred in the starting process which began from the starting inlet mode when the flow in the inlet duct is supersonic and culminated in the eventual unstarting inlet mode with a bow shock in front of the inlet and with the subsonic flow in its duct. [ABSTRACT FROM AUTHOR]

Numerical computations for studying the supersonic flows with a pseudo-shock wave were fulfilled. There was considered an axisymmetric duct including a funnel-shaped inlet, a throat section, a lengthened diffuser, and an outlet throttling section; the freestream flow with a Mach number M = 6 in front of the inlet was preset. There were applied the solvers including the Reynolds-averaged Navier-Stokes code and k-ω SST turbulence model for axisymmetric flows. The main subject of the investigation was determination of effects of the diffuser opening angle θd and the throttling level on forming the flow, gasdynamic and turbulent characteristics of the pseudo-shock wave. Data on variation of the turbulence viscosity along the duct length have shown the possibility of determination of the pseudo-shock wave termination in the diverging ducts instead of the usual method of determination of the pseudo-shock wave length by the distribution of the static pressure along the duct wall which is suitable just only for the non-diverging ducts. [ABSTRACT FROM AUTHOR]