Using Gas-Driven Shock Tubes to Produce Blast Wave Signatures.

Rubbel Kumar,Ashish Nedungadi

doi:10.3389/fneur.2020.00090

Abstract

The increased incidence of improvised explosives in military conflicts has brought about an increase in the number of traumatic brain injuries (TBIs) observed. Although physical injuries are caused by shrapnel and the immediate blast, encountering the blast wave associated with improvised explosive devices (IEDs) may be the cause of traumatic brain injuries experienced by warfighters. Assessment of the effectiveness of personal protective equipment (PPE) to mitigate TBI requires understanding the interaction between blast waves and human bodies and the ability to replicate the pressure signatures caused by blast waves. Prior research has validated compression-driven shock tube designs as a laboratory method of generating representative pressure signatures, or Friedlander-shaped blast profiles; however, shock tubes can vary depending on their design parameters and not all shock tube designs generate acceptable pressure signatures. This paper presents a comprehensive numerical study of the effects of driver gas, driver (breech) length, and membrane burst pressure of a constant-area shock tube. Discrete locations in the shock tube were probed, and the blast wave evolution in time at these points was analyzed to determine the effect of location on the pressure signature. The results of these simulations are used as a basis for suggesting guidelines for obtaining desired blast profiles.

Highlights

Detonation of explosive devices is typically associated with shrapnel and fire, both of which lead to visible injuries
Pressure traces were compared for this study at multiple probe locations based on non-dimensionalizing the probe’s distance from the driver/driven interface to the driver length, hereafter referred to as λ. These pressure traces allow us to compare the shocks at a variety of locations and understand where a Friedlander profile can be achieved based on driver length
Parametric studies were conducted using computational fluid dynamics (CFD) to characterize the primary overpressure blast environment created by a variety of laboratory shock tube designs

Summary

Introduction

Detonation of explosive devices is typically associated with shrapnel and fire, both of which lead to visible injuries. The increased prevalence of this injury has led to a heightened need to investigate both the mechanisms by which the injury occurs and the need for personal protective equipment (PPE) (e.g., helmet systems). To conduct these analyses effectively, it is important to replicate the blast overpressures experienced by warfighters in theater, through either blast testing or laboratory-based methods. Laboratory test methods using shock tubes offer more controlled, repeatable, and less expensive platforms for assessing blast traumatic brain injuries (bTBI) and performance of PPE. Shock tubes can be configured to generate blast signatures representative of free-field events [3]

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Conclusion