Experiments on the Starting Process in a Ludwieg Tube

An experimental investigation of the starting process in the Ludwieg tube, an intermittent type tube wind-tunnel, was conducted with emphasis on the effects of nozzle-test section geometry. In particular the semi-open and closed jet configuration was studied. Dry air at 1.0 and 2.0 atm pressure and room temperature was used in the supply tube and a quick opening diaphragm located downstream of the nozzle and test section was employed to initiate the flow. Spark shadowgraph pictures, high-speed shadowgraph movies, streak interferograms, and pressure measurements were made in M 1.67 and 3.0 continuously expanding nozzles and M 1.6 and 2.5 parallel flow nozzles. Results show that the nozzle-test section geometry significantly affects the starting process in the M 1.60 and 1.67 nozzles. Adverse pressure and density gradients were measured in the nozzle during the starting process.