Computational Fluid Dynamics Analysis of Blast Wave Interaction With Head and Helmet

Blast waves are generated upon release of a large amount of energy in few milliseconds. Upon release, these high pressure waves propagate rapidly and interact with human head and lead to severe traumatic brain injury (TBI). Understanding the mechanics of blast flow would allow us to develop effective tools to protect the head against these shockwaves. Military helmets are known as the most effective tool for protecting the soldier’s head against blast threats. However, due to the complicated nature of the shockwave development and propagation, as well as its interaction with head and helmet, the efficiency of helmets is still in question. The major problem with using helmets under blast loading is the entrapment of blast shockwaves inside the helmet gap and its reflection from the interior of the helmet’s shell. Moreover, development of an amplified pressure region at the opposite side of the incoming blast waves, referred to as the underwash effect of helmets has raised some concerns. To this end, we performed a computational fluid dynamics (CFD) analysis to better understand the mechanism of the blast shockwave interaction with head, as well as the effect of the helmet on the alteration of flow mechanics. The compressible, turbulent blast flow was simulated in ANSYS CFX by releasing the air from a high-pressure domain into the low-pressure one (at ambient pressure). The un/protected heads were exposed to an identical blast overpressure of 520 kPa in a frontal open blast scenario. Pressure contours and velocity profiles were recorded at several time instances for both unprotected and helmeted heads. Our primary results revealed that the change of the flow momentum inside the helmet gap, the reunion of the blast flow inside the gap as well as the development of adverse pressure gradient (and hence recirculating flow region) at the rear side of the head are the major reasons leading to this adverse phenomenon.