Starting a Convergent–Divergent Nozzle with a Busemann Diffuser

Abstract The problem of starting a convergent–divergent nozzle with a Busemann diffuser that provides a given air heating is solved. The starting simulates the nozzle acceleration in still air to a certain supersonic Mach number. The influence of viscosity on the diffuser flow is numerically investigated. The modeling is performed based on the two-dimensional non-stationary Navier−Stokes equations and the Godunov−Kolgan finite-difference scheme, adapted for calculating axisymmetric viscous gas flows. It is shown that starting the nozzle does not make it possible to obtain steady-state isentropic flow in form of a centered compression wave in the Busemann diffuser. The growth of the viscous layer leads to the formation of a system of inclined and normal shock waves moving upstream and creating zones of subsonic flow in the diffuser. The approach to the Busemann solution is not guaranteed to be reached even in the case of inviscid gas.