A computational fluid dynamics (CFD) study was carried out with data comparison to provide guidance for the control of open shock tube wave expansion to simulate field blast loadings for the conduct of biomechanical blast overpressure tests against surrogate test models. The technique involves the addition of a diffuser to the shock tube to prevent overexpansion before the shock wave impacts the test model. Mild traumatic brain injury (mTBI) has been identified as the signature injury for the conflicts in Iraq and Afghanistan, and blast overpressure from improvised explosive devices (IEDs) has been hypothesized as a significant mTBI risk factor. Research in the understanding of the mechanism of blast induced mTBI has been very active, which requires blast testing using animal and physical models. Full scale field blast testing is expensive. The use of shock tubes is clearly a viable cost effective laboratory method with many advantages. CFD simulations with data comparison show that without a diffuser, the shock wave exiting the tube tends to over expand producing an incident waveform with a short positive duration followed by a significant negative phase that is different from a Friedlander wave. However, the overexpansion effects can be mitigated by a diffuser. Shock tube tests also support the simulation results in which a diffuser improves the waveform from the shock tube. CFD simulations were validated by shock tube tests.

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