A semi-analytical model for the acoustic impedance of finite length circular holes with mean flow

Yang, Dong; Morgans, Aimee S.

doi:10.1016/j.jsv.2016.08.006

Cited by 42 publications

(57 citation statements)

References 29 publications

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“…Such holes were found to have the potential to generate as well as absorb acoustic energy, even in the low Strouhal number region. A theoretical model was recently developed based on the Green's function method to take the vortex-sound interactions both within and after the hole into consideration [19]. This model was able to predict the experimentally measured trends.…”

Section: Introductionmentioning

confidence: 99%

“…Other commonly used empirical models also neglect vortex-sound interaction within the neck and assume unconfined openings either side of it [3]. The analytical model developed in [19] uses cylinder Green's functions to calculate the acoustic field within and either side of a hole. It is therefore highly suitable for studying the effect of confined space on the overall acoustic response of short holes.…”

Section: Introductionmentioning

confidence: 99%

“…In Section 2, the cylinder Green's function method developed in [19], denoted CG in this paper, is briefly outlined and the expressions for the Rayleigh conductivity and energy absorption of a short hole opening to a confined space either side derived. A simplified version of the model for large expansion ratios is then developed by using a half-space Green's function, with this model denoted HSG.…”

Section: Introductionmentioning

confidence: 99%

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The acoustics of short circular holes opening to confined and unconfined spaces

Yang

Morgans

2017

Journal of Sound and Vibration

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The sound generated or absorbed by short circular holes with a mean flow passing through them is relevant in many practical applications. Analytical models for their acoustic response often ignore the fact that such holes open to a confined or finite space either side, or account for this e ect simply by adding an end mass inertial correction. The vortex-sound interaction within a short hole has been recently shown to strongly a ect the acoustic response at low frequencies [D.Yang and A.S.Morgans, J Sound Vib 384 (2016), pp.294 – 311]. The present study considers a semi-analytical model based on the Green’s function method to investigate how the expansion ratios either side of a short hole a ect the vortex-sound interaction within it. After accounting for expansions to confined spaces using a cylinder Green’s function method, the model is substantially simplified by applying a half-space Green’s function for expansions to large spaces. The e ect of both the up- and downstream expansion ratio on the acoustics of the hole is investigated. These hole models are then incorporated into a Helmholtz resonator model, allowing a systematic investigation into the e ect of neck-to-cavity expansion ratio and neck length. Both of these are found to a ect the resonator damping

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The acoustics of short circular holes opening to confined and unconfined spaces

Yang

Morgans

2017

Journal of Sound and Vibration

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“…3 does not depend on the resonance frequency, and the pressure loss coefficient ζ H gives the energy transfer from the acoustically-driven incompressible potential flow through the neck to the vortices that are periodically shed from the rim of the neck outlet. One can refer to [54] for a detailed investigation on the modeling of orifice impedance for a broad range of geometries and Strouhal numbers. Combining (2) and (3), one obtains the HH resonator impedance:…”

Section: Helmholtz Resonator (H)mentioning

confidence: 99%

Stabilization of acoustic modes using Helmholtz and Quarter-Wave resonators tuned at exceptional points

Bourquard

Noiray

2019

Journal of Sound and Vibration

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Acoustic dampers are efficient and cost-effective means for suppressing thermoacoustic instabilities in combustion chambers. However, their design and the choice of their purging air mass flow is a challenging task, when one aims at ensuring thermoacoustic stability after their implementation. In the present experimental and theoretical study, Helmholtz (HH) and Quarter-Wave (QW) dampers are considered. A model for their acoustic impedance is derived and experimentally validated. In a second part, a thermoacoustic instability is mimicked by an electro-acoustic feedback loop in a rectangular cavity, to which the dampers are added. The length of the dampers can be adjusted, so that the system can be studied for tuned and detuned conditions. The stability of the coupled system is investigated experimentally and then analytically, which shows that for tuned dampers, the best stabilization is achieved at the exceptional point. The stabilization capabilities of HH and QW dampers are compared for given damper volume and purge mass flow.

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“…The revised Rayleigh conductivity accounts for the length of the HR neck as a mass inertia correction to the Rayleigh conductivity for a short hole -a new model which accounts for vortex-sound interaction within the neck could also be incorporated [20,21]. Generally, mass, momentum and energy flux perturbations within the combustor can be written as…”

Section: Theoretical Modelmentioning

confidence: 99%