Keywords: Helmholtz resonators, flow effect, transmission loss, CFD, computational fluid dynamics, mean flow, acoustic attenuation performance, noise generators, acoustics
A two-dimensional computational study of the flow effect on the acoustic behaviour of Helmholtz resonators
Impact of mean flow on the acoustic attenuation performance of a Helmholtz resonator is investigated computationally. To determine the time-dependent flow field, two-dimensional unsteady, turbulent, and compressible Navier-Stokes equations are solved. Pressure obtained from the flow field is used to calculate the Helmholtz resonator's transmission loss at different velocities. Increasing the mean flow velocity in the main duct is shown computationally to reduce the peak transmission loss in general and force a shift in the fundamental resonance frequency to a higher value. These predictions are consistent with the trends observed in the experimental studies available in the literature. Also, at discrete Strouhal numbers, the simulations capture the flow-acoustic coupling which transforms the Helmholtz resonator essentially to a noise generator. The approach presented here demonstrates the ability of a numerical tool to study the complex interactions of the flow field with the acoustics of Helmholtz resonators effectively.