Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Parametric study of Helmholtz resonators in acoustic cavities
Submission Author:
Derick Fernandes , DF
Co-Authors:
Derick Fernandes, Manuel Barcelos Júnior
Presenter: Derick Fernandes
doi://10.26678/ABCM.COBEM2021.COB2021-0796
Abstract
Currently, there are several forms of noise attenuation and, whether passive or active, all have specific applications and limitations, and it is up to the designer to select which optimizes the desired result. One of these possibilities is to base on the system's resonance effects through Helmholtz resonator assemblies. However, such devices we must design with specific parameters for a given critical situation. A given resonator's geometry and dimensions restrict acoustic effects to a frequency range. Therefore, it is fundamental to develop an analytical methodology, prior to the experimental and numerical analyses, that allows the efficient design of resonators and their matrix configurations for a specific acoustic system. Thus, based on known mathematical models, this paper develops a theoretical study of the impact on resonance frequency and sound pressure levels by changing layouts and parameters such as neck radius and length, cross-section geometries, cavity volume, and series or parallel dispositions of Helmholtz resonators. The study establishes a mass-spring analogy for the volume of fluid in the resonator cavity. Newton's laws are applied to obtain the system's oscillatory dynamics, thus calculating its stiffness and resonance frequency. Subsequently, we develop an analytical methodology for the evaluation of resonator matrix configurations to quantify the sound transmission loss and the total acoustic impedance of different systems in continuous cross-section cavities without internal flow and in cavities with constant pressure and volume flow at the duct intersection. An observation of the initial results shows that the resonance frequency decreases with the neck length increasing the resonator's effect and the increasing cavity volume while keeping the effective neck length fixed. For the matrix configurations, the growing behavior of both the total system impedance and the sound transmission loss is observed directly to the number of resonators, tending to stabilize after a finite number of devices in parallel.
Keywords
Helmholtz resonators, Parametric Study, Acoustic resonance, Series resonance, parallel resonance, Aeroacoustics
