A Novel Method to Minimize Secondary Loading in a Closed-End Shock Tube

The development of shock tubes and understanding of shock wave propagation and its interaction with a model is of significant interest in various domains. In this context, shock tubes effectively recreate the field explosion in controlled laboratory conditions and ensure safety, low cost and repeatability. The blast wave simulators (BWS) are operated in a reflective (for barrier wall, blast absorbent material, etc.) and diffractive (for biofidelic head and torso, In-vivo, etc.) mode. The side wall reflections in refractive mode and end wall reflections from the model in reflective mode shock tube cause secondary loading to the model. In this study, a reflection wave eliminator (RWE) with a flap assembly was developed to minimize secondary loading in closed-end shock tubes, and its performances are discussed. As the first cycle of shock wave crosses the RWE, it will open the flap assembly and helps in minimizing the successive cycles of shock waves. The effect of RWE location and the number of flap openings on shock wave parameters, such as positive peak overpressure and impulse, for the case of two different shock tubes length, such as 3.3 m and 5.3 m, has been studied. It was observed that the peak overpressure reduction in the secondary shock wave because of single flap RWE at the model location is 71.31% and 88.12% for 3.3 m and 5.3 m long shock tubes, respectively. The secondary loading of the model in closed-end shock tubes can be significantly reduced by tuning the standard shock tube using the RWE proposed in this study.