Investigation of the effects of volume change on flow structure and acoustic in a silencer

Abstract

This study numerically examined the propellant flow from gunfire using the kω-SST turbulence model and their sound attenuation using the Ffowcs-Williams and Hawkins equations (FW-H). For simulation, a pressure-based solver and 3D axisymmetric geometry were used. The second-order implicit time approach and the second-order upwind scheme spatial discretization were used in the simulation. The maximum exit pressure was 3.748 MPa for the suppressor with a length of 70 mm and diameter of 20 mm. However, when the diameter suppressor increased by 1/6, the maximum exit pressure was reduced to 3.4961 MPa. When the length increased by 1/6, the maximum pressure became 3.3636 MPa. Lastly, when the diameter and length were increased by 1/6, the maximum exit pressure became 3.177 MPa. For this suppressor, 20.835 dB (12.29%) sound pressure level attenuation was achieved with 16.823 MPa (84.115%) overpressure reduction and 484.86 K or 32.32% temperature reduction. Generally, the attenuation increased with the increase in the suppressor’s internal volume.