The starting process in a hypersonic nozzle

This paper describes an experimental study of the starting process in a reflected-shock tunnel, and compares the results with numerical calculations reported previously (Smith 1962). It is shown that an unsteady expansion wave dominates the transient flow, and the shock-wave system plays a minor role. The effects of initial pressure in the nozzle were investigated, and the behaviour of the secondary shock wave was noted. It was found that initial pressures larger even than the steady-flow static pressure can be tolerated without prolonging the starting process, despite the presence of a strong secondary shock wave. Other analyses, based on the ‘steady-state’ model of the starting process, are discussed and shown to give an unrealistic description of the flow field.