Influence of diaphragm opening process on shock tube flow

The diaphragm opening process in a shock tube is far from ideal in practical scenarios as it is highly dependent on several factors. A non-ideal diaphragm rupture can result in a three-dimensional flow due to reflections and interactions of secondary waves behind the shock front. The main aim of the present study is to investigate the effects of non-ideal diaphragm rupture on shock tube performance. Experiments are carried out in the Low-Pressure Shock Tube (LPST) at KAUST using argon as driven gas at P₅ = 1.33 – 2.06 bar and T₅ = 1090 – 2142 K. Optical windows installed in the end walls of the driver and driven sections facilitate high-speed imaging of the diaphragm opening process. The thickness of the cellophane diaphragm used, the location of the diaphragm cutter, and the flow rate of driver gas prior to diaphragm rupture are varied to obtain different diaphragm opening configurations. We will present the results of our investigation on the dependence of the rate of diaphragm opening and the diaphragm opening time on the post-shock pressures and temperatures obtained in the shock tube. The abnormal effects of the slow driver gas filling and asymmetrical diaphragm opening on the pressure profile during the test time will also be presented.