Aeroacoustic simulation of a flow-excited Helmholtz resonator using OpenFOAM

The flow-excited Helmholtz resonator is a classical example of acoustical resonance induced by fluid flow. Similar phenomena of sound production are also responsible for the noise amplification in ventilation ducts with side branches and the sound generation of air reed wind instruments, for example. In the past few years several studies investigating the fluid flow and the acoustical feedback in the Helmholtz resonator were published. These examinations include analytical treatments, experiments, and simulations based on discrete vortex dynamic models and computational fluid dynamics. This paper presents the aeroacoustic simulation of a Helmholtz resonator excited by grazing flow. Numerical computations at different flow speeds are performed by solving the compressible Navier-Stokes equations using the finite volume method implemented in the OpenFOAM software package. First, shear layer oscillations are examined without acoustical feedback in order to determine the frequency of the hydrodynamic modes and to estimate the convection speed of perturbations. Then, the acoustical response of the resonator is computed and the natural frequency and quality factor of the resonator are determined. Finally, flow-induced resonance is simulated at different flow speeds and the results are compared with that of other models published previously