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COBEM 2019
25th International Congress of Mechanical Engineering
Time domain response of Helmholtz resonators under linear and nonlinear excitation in subsonic flow
Submission Author:
Emerson Almeida Camargo , DF , Brazil
Co-Authors:
Emerson Almeida Camargo, Marcus Vinicius Girão de Morais, Adriano Todorovic Fabro
Presenter: Emerson Almeida Camargo
doi://10.26678/ABCM.COBEM2019.COB2019-1415
Abstract
Helmholtz resonators play an important role in acoustic treatment nowadays. Typically, turbofans use acoustic liners, that can be described as arrays of Helmholtz resonators. This work aims to study the response of resonators ender different conditions. The simulations were carried out with the Virtual Aeroacoustic Tunnel (VAT), a {\it in-house} code developed at Computational Aeroacoustic Laboratory (CAALab) of University of Brasilia. A test case of a Helmholtz resonator under subsonic flow is simulated considering no pressure source, a 148 dB and 168 dB SPL at 566 Hz. The results show the time domain response of the resonator under the different operational conditions. The simulation with no pressure source shows the characteristic frequency of the Helmholtz resonator while and both simulations with the pressure source present an almost linear behaviour for the first case, i.e., the dominant response frequency is the same as the source and the second case presents a typical non-linear response due to the presence of the vorticity effects. The present test case can effectively simulate the linear and non-linear effects of a subsonic flow of a typical Helmholtz resonator and can be used for further investigation. Moreover, the conducted simulations presented that an increase in the sound pressure level leads the resonator from a linear behaviour to a nonlinear one, as described in the literature.
Keywords
Helmholtz resonator, Acoustic Liner, VAT, Euler equations
