Effects Of Geometry On The Resonance Frequency Of Helmholtz Resonators

Chanaud, Robert

doi:10.1006/jsvi.1994.1490

Cited by 176 publications

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“…Acoustically tunable porous surfaces can be designed building upon traditional acoustic liners by tweaking two simple features: the size of the Helmholtz cavities can, in fact, be adjusted to resonate at the characteristic time scales of the flow, following (26); the porosity of the surface coatings and orifice sizes can be adjusted to achieve the desired permeability. Simple parametrizations such as the ones provided in Chanaud 44 can be used to relate the characteristic resonant frequency (controlled by the imaginary part of the impedance in (15)) with all the geo-metrical features of the resonator, including the orifice size. The latter also regulates the effective surface permeability, inversely proportional to the impedance resistance in (15).…”

Section: Discussionmentioning

confidence: 99%

Compressible turbulent channel flow with impedance boundary conditions

Scalo

Bodart

Lele³

2015

Physics of Fluids

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OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. This is an author's version published in : http://oatao.univ-toulouse.fr/13597 We have performed large-eddy simulations (LES) of isothermal-wall compressible turbulent channel flow with linear acoustic impedance boundary conditions (IBCs) for the wall-normal velocity component and no-slip conditions for the tangential velocity components. Three bulk Mach numbers, M b = 0.05, 0.2, 0.5, with a fixed bulk Reynolds number, Re b = 6900, have been investigated. For each M b , nine different combinations of IBC settings were tested, in addition to a reference case with impermeable walls, resulting in a total of 30 simulations. The IBCs are formulated in the time domain according to Fung and Ju 1 . The adopted numerical coupling strategy allows for a spatially and temporally consistent imposition of physically realizable IBCs in a fully explicit compressible Navier-Stokes solver. The impedance adopted is a three-parameter, damped Helmholtz oscillator with resonant angular frequency, ω r , tuned to the characteristic time scale of the large energy-containing eddies. The tuning condition, which reads ω r = 2πM b (normalized with the speed of sound and channel half-width), reduces the IBC's free parameters to two: the damping ratio, ζ, and the resistance, R, which have been varied independently with values, ζ = 0.5, 0.7, 0.9, and R = 0.01, 0.10, 1.00, for each M b . The application of the tuned IBCs results in a drag increase up to 300% for M b = 0.5 and R = 0.01. It is shown that for tuned IBCs, the resistance, R, acts as the inverse of the wall-permeability and that varying the damping ratio, ζ, has a secondary effect on the flow response. Typical buffer-layer turbulent structures are completely suppressed by the application of tuned IBCs. A new resonance buffer layer is established characterized by large spanwise-coherent Kelvin-Helmholtz rollers with a well-defined streamwise wavelength, λ x , traveling downstream with advection velocity c x = λ x M b . They are the effect of intense hydro-acoustic instabilities resulting from the interaction of high-amplitude wall-normal wave propagation at the tuned frequency f r = ω r /2π = M b with the background mean velocity gradient. The resonance buffer layer is confined near the wall by (otherwise) structurally unaltered outer-layer turbulence. Results suggest that the application of hydrodynamically tuned resonant porous surfaces can be effectively employed in achieving flow control.

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Section: Discussionmentioning

confidence: 99%

Compressible turbulent channel flow with impedance boundary conditions

Scalo

Bodart

Lele³

2015

Physics of Fluids

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“…The value of the resistance is furthermore dependent on the flow-rate of the air, however, in the case of small acoustic pressures (compared to the atmospheric one), which is the case in the discussed system, this effect can be neglected (Chanaud, 1994; Davies, Webster, 2010).…”

Section: Acoustic Approach To the Volume Measurement Problemmentioning

confidence: 96%

“…In the electrical model, the resistance R corresponds to the dissipation of energy due to the viscosity of gas; the capacitance C reflects the volumes of the connected resonators, while the inductance L is a representation of the properties of the neck, connecting both resonators. This is true when the size of the resonator is smaller compared to the length of the resonant acoustic wave frequency (Chanaud, 1994;Chiu, 2012).…”

Section: Acoustic Approach To the Volume Measurement Problemmentioning

confidence: 99%

Acoustic System of Determining the Instantaneous Volume of the Blood Part of the Ventricular Assist Device POLVAD-EXT

Konieczny¹,

Pustelny²,

Opilski³

et al. 2015

Archives of Acoustics

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The paper presents the results of investigations concerning the noninvasive method of estimating the actual volume of the blood chamber of the POLVAD-EXT type ventricular assist device (VAD) during its operation. The proposed method is based on the principle of Helmholtz's acoustic resonance. Both the theory, main stages of the development of the measurement method as well as the practical implementation of the proposed method in the physical model of the POLVAD-EXT device are dealt with. The paper contains the results of static measurements by means of the proposed method (conducted at the Department of Optoelectronics, Silesian University of Technology) as well as the dynamic measurements taken at the Foundation of Cardiac Surgery Development (Zabrze, Poland) with the professional model of the human cardiovascular system. The results of these measurements prove that the proposed method allows to estimate the actual blood chamber volume with uncertainties below 10%.

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“…The study [13] deals with the effect of orifice geometry on the resonance frequency of Helmholtz's resonators. Helmholtz's theoretical formula for calculating resonant frequency f H is as follows:…”

Section: Helmholtz's Resonatorsmentioning

confidence: 99%

Resonance Effect of Nanofibrous Membrane for Sound Absorption Applications

Kalinová¹

2017

Resonance

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Nanofibrous layers have unique acoustic properties due to the large specific surface area of the nanofibers, where viscous losses may occur and also the ability of the nanofiber layer to resonate at its own frequency. The resonance membrane is then, upon impact of sound waves of low frequency, brought into forced vibrations, whereby the kinetic energy of the membrane is converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air, and possibly with other layers of material arranged in its proximity, and part of the energy is also transmitted to the frame, by which means the vibrations of the resonance membrane are damped. When sound waves hit the nanofiber membrane, they introduce forced vibrations in the case of resonance which have maximal amplitude. The principle of the technology is achieved by the synergy of perforated plate in the form of a cavity resonator with nanofibrous layer in the form of resonant membrane. The parameters of the resonant nanofibrous membrane together with the shape and volume of the perforations then determine which sound frequencies will be damped and to what extent.

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Effects Of Geometry On The Resonance Frequency Of Helmholtz Resonators

Cited by 176 publications

References 0 publications

Compressible turbulent channel flow with impedance boundary conditions

Compressible turbulent channel flow with impedance boundary conditions

Acoustic System of Determining the Instantaneous Volume of the Blood Part of the Ventricular Assist Device POLVAD-EXT

Resonance Effect of Nanofibrous Membrane for Sound Absorption Applications

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