Starting phenomena in a supersonic tube wind tunnel

An experimental study has been performed of the unsteady processes in the starting period of a supersonic Ludwieg tube, a device which operates like an intermittent supersonic wind tunnel. A quick opening diaphragm located downstream of the nozzle initiates the flow. Pressure and density measurements are made in a variety of ways in Mach number 1.67 and 3.0 nozzles. For the starting conditions treated, supersonic flow is established in the nozzle without producing shock waves. Various time dependent functions are observed in the adjustment of gasdynamic parameters to their steady supersonic values. These changes of pressure etc., include undershoots, overshoots, and other variations of the final steady-state values. Calculations based on an assumed zero-length nozzle do not adequately predict starting times and pressures.