Computational Fluid Dynamics Analysis of the Acoustic Performance of a Typical Firearm Silencer

In this work, a firearm silencer is modeled without and with heated gas particles to capture its effect on the silencer performance. A well-known phenomenon in firearm suppressors is the so-called “first round pop”, when the air of an unused, empty suppressor interacts with the flames produced by the first bullet fired through it, the firearm suppressor produces a very loud pop that still requires hearing protection. Subsequent shots are quieted by the silencer geometry as a consequence of the hot gases filling the interior. This effect is investigated using Computational Fluid Dynamics (CFD), integrating a Volume of Fluids (VOF) model to incorporate the gunpowder products within the silencer. First, an unsuppressed firearm is simulated to obtain the baseline sound levels of a 9mm bullet using known ballistics data. Then, the model will be run with the silencer geometry, referencing a Yankee Hill Machine Co. Model R9 Suppressor for 9mm firearms, filled with ambient temperature air. Then, once the heating and gas fraction values are obtained from this first round run, models will be run using the heated gas values as initial conditions within the suppressor volume to observe the heated suppression in action.