Acoustic and aerodynamic dissipations induced by a sound wave‐impacted Helmholtz resonator

Abstract

The purpose of the work introduced herein is to study the dissipation of the acoustic energy carried by sound waves, by a Helmholtz resonator. Two‐dimensional direct numerical simulations (DNS) are performed with the CEDRE code, a Navier‐Stokes equations solver developed by Onera, for a resonator with a 0.8 × 0.8 mm square opening. The incident sound pressure level (SPL) varies between 100 dB and 150 dB: it is checked that when the SPL is low, the acoustic energy is dissipated in the resonator opening by viscous wall friction, whereas when the SPL is high, the acoustic energy is converted in kinetic energy carried by micro‐vortices induced at the opening mouths. However, when the SPL takes intermediate values, both mechanisms coexist. Thus, for each case, we aim at splitting the aeraoacoustic field into respective acoustic and aerodynamic contributions, and at evaluating the ratio between these two distinct mechanisms in order to quantify their relative weight on the global dissipation. Our results are compared with those obtained by Tam et al. for the same geometry. A three‐dimensional study for a Helmholtz resonator with a cubic opening is eventually considered.