An extended neck versus a spiral neck of the Helmholtz resonator

Cai, Chenzhi; Mak, Cheuk Ming; Shi, Xiaofeng

doi:10.1016/j.apacoust.2016.08.020

Cited by 78 publications

(19 citation statements)

References 17 publications

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“…The shear separation is also significantly different. 32 This may be due to the fact that nonslip boundary conditions 33 hold on the neck surface.…”

Section: Resultsmentioning

confidence: 99%

Numerical studies of transmission loss performances of asymmetric Helmholtz resonators in the presence of a grazing flow

Pan

Guan

2018

Journal of Low Frequency Noise, Vibration and Active Control

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As a typical noise-attenuating device, Helmholtz resonators are widely implemented in aero-engines and gas turbines to decrease the transmission of acoustic noise. However, an asymmetric Helmholtz resonator could be designed and implemented due to the limited space available in the engines. To examine and optimize the noise-attenuating performances of the asymmetric resonator, comparison studies are performed. For this, a two-dimensional frequency-domain model of a cylindrical duct with a grazing flow is developed. An asymmetric Helmholtz resonator is attached as a side branch. The model containing the linearized Navier-Stokes equations is validated first by comparing the predicted results with the experimental ones available in the literature. Further validation is conducted by comparing the results of an asymmetric resonator with the analytical ones available in the literature. The effects of (1) neck offset distance from the center of the resonator cavity denoted by e c =a s and (2) the grazing flow Mach number M u are evaluated. It is shown that as the grazing flow Mach number is increased, the resonant frequencies and the maximum transmission losses are dramatically varied for a given e c =a s. As e c =a s is increased from 0 to 0.5 and M u ! 0:1, the resonant frequencies and the maximum transmission losses are increased. However, when M u is lower than 0.07, i.e. M u 0:07, the transmission loss performances are almost unchanged with e c =a s increased. The optimum design of the asymmetric resonator is shown to give rise to the resonant frequency being shifted by 10% and 2-5 dB more transmission loss at higher Mach number. Finally, visualization of vortex shedding formed at the neck of the asymmetric resonator confirms that acoustical energy is transformed into kinetic energy and absorbed by the surrounding air. This study opens up a numerical design approach to optimize an asymmetric resonator.

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“…The shear separation is also significantly different. 32 This may be due to the fact that nonslip boundary conditions 33 hold on the neck surface.…”

Section: Resultsmentioning

confidence: 99%

Numerical studies of transmission loss performances of asymmetric Helmholtz resonators in the presence of a grazing flow

Pan

Guan

2018

Journal of Low Frequency Noise, Vibration and Active Control

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“…Similar investigations and analytical calculations should be carried out for the other shapes of resonators in the future such as cylindrical and rectangular, which is a very important task, according to the existence of the publications. Moreover, investigations [7] show that the shape of the neck also has a significant effect on the measurement results, which also requires careful study.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, a detailed research of previously unexplored properties of resonators will make it possible to improve the algorithms for the development of metamaterials, to discover additional parameters with which it is possible to control the characteristics of the metamaterial. The influence of Helmholtz resonator geometry on its characteristics was researched in many works (example, [6,7]).…”

Section: Introductionmentioning

confidence: 99%

Research of the Resonance Properties of Helmholtz Resonators

et al. 2020

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The object of research. Process of oscillation of the Helmholtz resonators. Investigated problem. Differences between some formulas for the calculation of the resonant frequency of the Helmholtz resonator and the most accurate of them were established. The effect of acoustic design on the Helmholtz resonator frequency value and influence of the attached air mass between the neck of the Helmholtz resonator and free field were investigated. The main scientific results. As a result of a numerical experiment, analytical ratios were obtained that allow obtaining the most accurate results. One of them is the most optimal for calculating the resonator resonant frequency in a free field, and in this case, less than 1 % inaccuracy level can be achieved, given that r/R<0.25. Other one allows to achieve the same low inaccuracy level for a resonator located in an acoustically rigid shield, given that r/R<0.25. Research has shown that the location of the resonator in an acoustically rigid shield leads to significant changes in natural resonance frequency value. The area of practical use of the research results. The detailed research of previously unexplored properties of resonators will make it possible to improve the algorithms for the development of metamaterials, to discover additional parameters with which it is possible to control the characteristics of the metamaterial. Scope of the innovative technological product. Such resonators are used as the basic elements in metamaterials, as structural elements of the sound-absorbing panels, in acoustic mufflers.

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“…Cai et al [25] numerically evaluated the acoustic performance of a resonator with an extended neck and a spiral neck in an attempt to improve the performance of noise attenuation of a low-frequency Helmholtz resonator in a limited space. The chamber volume was kept constant and the neck length was increased.…”

Section: Introductionmentioning

confidence: 99%

Effects of variable-volume Helmholtz resonator on air mass flow rate of intake manifold

Hanriot

Queiroz

Maia

2019

J Braz. Soc. Mech. Sci. Eng.

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The application of geometric modifications to the intake manifold to improve engine breathing provides positive results using different strategies. Helmholtz resonators (HR) are one of the most basic acoustic models and are widely used in engineering applications. Most of the works presented in the literature focus on the use of HR in the fields of acoustics. The present work experimentally investigates pulsating flow characteristics of the engine intake manifold and the effects of a Helmholtz resonator with variable internal volume. In this paper, acoustic studies were used to model the intake manifold and to develop a complex expression to determine the natural frequency of the system. The model included the primary and secondary intake pipes and the resonator. Experiments were conducted on a straight intake pipe connected to an engine cylinder head mounted on a test flow bench, especially designed for fluid dynamic studies of engine intake systems with unsteady flow conditions. Using electronic controls, the internal volume of the resonator was varied and adjusted according to the frequency of the valves as well as the natural frequency of the intake manifold. The natural frequency of the system was determined from a numerical model of the intake manifold. The results showed the internal volume of the resonator and frequency tuning affect the intake air mass flow rate at a wide range of camshaft velocities. For a fixed volume, the average increase of the mass flow rate was 17.8%, and when the volume was adjusted according to valve frequency, the average increase was 24.7%. The highest intake air mass flow rate was increased 31.5% when the resonator was tuned to the frequency of the system.

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An extended neck versus a spiral neck of the Helmholtz resonator

Cited by 78 publications

References 17 publications

Numerical studies of transmission loss performances of asymmetric Helmholtz resonators in the presence of a grazing flow

Numerical studies of transmission loss performances of asymmetric Helmholtz resonators in the presence of a grazing flow

Research of the Resonance Properties of Helmholtz Resonators

Effects of variable-volume Helmholtz resonator on air mass flow rate of intake manifold

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