Numerical investigation of ventilation efficiency in a Combat Arms training facility using computational fluid dynamics modelling.

Firing ranges critically depend on ventilation systems to minimize the exposure of personnel to ammunition refuse. A numerical analysis utilizing a computational fluid dynamics (CFD) method was used to simulate the ventilation system and predict airflow patterns within a 122-foot long, military firing range housing 21 firing stalls. The intent for this model was to identify back circulation causing firing emissions to entrain in occupied areas. Measured values at several locations within the facility were used for either input values in the model or for validation of the model solution. The analysis evaluated massless particles released at three heights to correspond with standing, kneeling, and prone firing positions. Additional predictions were completed using the recommended technical guidance for ventilation of small arms firing ranges to compare against flow dynamics of the current system. The results revealed particles circulating back behind the shooter and into the personnel occupied area. Lower supply air velocities correspond to more uniform flow and successful movement of particles downrange in the small arms firing range under investigation. The ventilation air velocity at the firing line recommended by the design guide was not achieved consistently despite the supply air velocity being set to design guide values. Overall, the results demonstrated that CFD models are useful aides for optimizing supply air velocities in current firing range facilities and for evaluating and developing design standards that provide the proper ventilation required for the health and safety of building occupants. • Developed computational model simulating firing emissions exposure due to ventilation air flow in a small arms, military, firing range and verified predictions with measured data. • Developed additional models using US Air Force design guidelines to showing ammunition particulates were not removed when standards were met. • Air flow velocities at the firing line per design guide were not achieved even when the recommended supply air flow was specified. • Firing emissions simulated particulate circulated into occupied area at actual supply air velocities and when velocities were set within the higher design standard velocity range. • Simulation predictions indicate occupants may be exposed to firing emissions from lead-free frangible ammunition which could be the cause of reported health effects by personnel. [ABSTRACT FROM AUTHOR]