STUDIES OF THE TRANSIENT FLOWS IN HIGH ENTHALPY SHOCK TUNNELS

The nature of high enthalpy shock tunnels dictates that only very limi ted run time can be achieved during experiments. Due to the extreme fl ow conditions and the severe time constraint involved, it is very diff icult to conduct diagnostic measurements to determine the flow conditi on produced in the facilities. A series of numerical studies has there fore been carried out to provide a quantitative description of the tra nsient flow in the shock tunnel. The flows in the HEG shock tunnel are analyzed using time-dependent viscous computations. The studies focus ed on the events subsequent to shock reflection at the downstream end of the shock tunnel, namely, the reservoir and the nozzle regions. For the shock tube, the interactions of the reflected shock with the wall boundary layer and the contact surface are examined for their contrib ution to driver gas contamination and the generation of flow disturban ces. This includes interaction with the reflecting wall geometry, that is, in the presence of the nozzle entrance and ''particle stopper''. For the starting flow in the nozzle, the propagation of the initial sh ock system and the development of the boundary layers during the start ing transient are examined and the time required to established the st eady flow is analyzed to help determine the proper ''test window'' in the experiments.