Alagappan Ponnalagu

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.

Blast wave simulators (BWS) are shock tubes capable of generating shockwaves with Friedlander profile (typical profile observed during free field explosion).They have primary importance in blast-related research.The pressure–time profile parameters, such as peak overpressure, positive time duration, and decay coefficient of the shockwave, depend on the shock tube parameters (STPs) such as driver length, driven length, and burst pressure.We can generate shockwaves with the desired pressure–time profile by effectively tuning the STP.This study experimentally investigates the effect of driver length on the pressure–time profile of a shockwave generated by a blastwave simulator.Increasing the driver length increases the positive phase duration and peak overpressure at all probe locations.Also, it increases Friedlander profile formation distance.Further, a finite element model for shock tube is developed in ABAQUS/Explicit and the numerical results are compared with the experimental observations.The developed numerical model can predict the observed pressure–time profile with reasonable accuracy, so that it can be used for further parametric studies in the design of blast wave simulators.