Numerical shape optimization of photoacoustic resonators

Kost, Bernd; Baumann, Bernd; Germer, Markus; Wolff, Marcus; Rosenkranz, Marco

doi:10.1007/s00340-010-4170-z

Cited by 31 publications

(13 citation statements)

References 12 publications

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“…Certainly, the proper design optimization for a so miniaturized cell should be performed with the help of an accurate 3D numeric simulation, which takes into account features (for instance, influence of the cell sensor on the resonant acoustic standing wave) important for the consideration. The COMSOL Multiphysics software package seems to be a suitable tool, which can be applied for such purposes [31][32][33][34].…”

Section: Suggestionsmentioning

confidence: 99%

A miniaturized prototype of resonant banana-shaped photoacoustic cell for gas sensing

Ulasevich

Gorelik

Kouzmouk

et al. 2013

Infrared Physics & Technology

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A resonant photoacoustic cell intended for laser-spectroscopy gas sensing is represented. This cell is a miniature imitation of a macro-scale banana-shaped cell developed previously. The parameters, which specify the cavity shape, are chosen so as not only to provide optimal cell operation at a selected acoustic resonance but also to reduce substantially the cell sizes. A miniaturized prototype cell (the volume of acoustic cavity of ~ 5 mm 3 ) adapted to the narrow diffraction-limited beam of near-infrared laser is produced and examined experimentally. The noise-associated measurement error and laser-initiated signals are studied as functions of modulation frequency. The background signal and the useful response to light absorption by the gas are analyzed in measurements of absorption for ammonia in nitrogen flow with the help of a pigtailed DFB laser diode oscillated near a wavelength of 1.53 µm. The performance of prototype operation at the second longitudinal acoustic resonance (the resonance frequency of ~ 32.9 kHz, Q-factor of ~ 16.3) is estimated. The noise-limited minimal detectable absorption normalized to laser-beam power and detection bandwidth is ∼ 8.07·10 -8 cm -1 W Hz -1/2 . The amplitude of the background signal is equivalent to an absorption coefficient of ~ 2.51·10 -5 cm -1 . Advantages and drawbacks of the cell prototype are discussed. Despite low absorption-sensing performance, the produced miniaturized cell prototype shows a good capability of gas-leak detection.

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Section: Suggestionsmentioning

confidence: 99%

A miniaturized prototype of resonant banana-shaped photoacoustic cell for gas sensing

Ulasevich

Gorelik

Kouzmouk

et al. 2013

Infrared Physics & Technology

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“…The photoacoustic effect occurs when a laser is mechanically chopped or agreement with measurements. Simulation is also well suited in an optimization approach where the maximum of signal is searched [5][6][7]. We present here the complete optimization and characterization of a photoacoustic cell using FEM.…”

Section: Introductionmentioning

confidence: 99%

Optimization and complete characterization of a photoacoustic gas detector

et al. 2014

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periodically modulated in and out an absorption line of the studied molecule. During the relaxation process, energy is mainly transferred by collision to the surrounding molecules. A local change of temperature is then induced along the laser beam, and a standing wave is created inside the cell.Photoacoustic cells are often used in resonant mode in order to take advantage of the enhancement of the acoustical signal. The resonator shape directly affects the strength and the distribution of these pressure variations. To take full benefits of the sound wave amplification, the quality factor, the resonant frequency and the peak amplitude at resonance are the three main parameters to be determined. These three parameters are usually experimentally determined from the cell response:U is the measured voltage of the microphone (V), R M its sensitivity (V/Pa), W the optical power of the laser (W), c the gas concentration and K the absorption coefficient (cm −1 ). The maximum value of R c (ω) is often referred as the cell constant. This constant is used to determine the detection limit of the photoacoustic spectrometer. In order to enhance this detection limit, one must be able to predict the cell response.Positions of resonant frequencies and Q-factors can be calculated for simple resonant volume where analytic solution exists [2]. For more complex cells, electric analogy can also be used to investigate the cell response [3]. Finite element method (FEM) presents the ease of use of a computational calculation and has already demonstrated its capabilities for the simulation of the photoacoustic cell characteristics. Baumann et al. [4] predicted the resonant frequencies and Q-factors of a T-shaped cell with a goodAbstract We report the complete designing process and realization of a photoacoustic spectrometer. In a first step, the cell design is optimized in order to achieve maximum cell constant and working frequency using a finite element method. Technological and integration constraints are used to define dimensional constraints on the cell. In a second step, a dedicated optical bench is presented along with the photoacoustic cell. The resonator response is then measured using a quantum cascade laser for methane detection and condenser microphones as detectors. The system detection limit is also discussed as it depends not only on the cell response but is also a combination of parameters linked together: environmental noise, microphones characteristics and cell conception. The gas flow required in a dynamic operation of the sensor degrades the detection limit regardless of the microphones quality. Choices on cell conception to minimize gas flow noise are discussed.

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“…Sound field inside a cavity depends on the cavity shape, which either impacts on the sound distribution in an acoustic system, or affects the coupling between the cavity and a surrounding flexible wall [Zheng and Wei, 2013;Geng and Li, 2012; S. Zhang & L. Cheng Chen et al, 2012] in a vibro-acoustic system [Fahy and Gardonio, 2007]. Typical examples include the shape optimization of the car body to improve the interior sound distribution in the acoustic design of automobile [Marburg and Hardtke, 2001;Koo et al, 1998]; design of inner partitions in cavities [Succi, 1987]; optimization of internal partitions in mufflers [Lee and Kim, 2009;Chiu and Chang, 2008;Mimani and Munjal, 2011] or resonators [Kost et al, 2011] etc. Therefore, topological or shape optimization of acoustic cavities is of significant relevance to both scientific research and engineering applications.…”

Section: Introductionmentioning

confidence: 99%

Shape Optimization of Acoustic Enclosures Based on a Wavelet–Galerkin Formulation

Zhang

2015

Int. J. Appl. Mechanics

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The problem of the shape optimization of acoustic enclosures is investigated in this paper. A general procedure, comprising a Wavelet–Garlerkin formulation and a so-called vertex-driven shape optimization is proposed to deal with the general problem of internal sound field prediction and the optimization of the boundary shape. It is shown that, owing to the compactly supported orthogonal property and the remarkable fitting ability, Daubechies Wavelet can be used as a global basis to approximate the unknown sound field on a relatively large interval globally instead of piecewise approximation like most of element based methods do. This feature avoids meshing the boundary of the enclosure, although vertex points are needed to define the boundary shape, whose positions keep updating during the shape optimization process. A rectangular enclosure is used as benchmark to assess and validate the proposed formulation, by investigating the influence of some key parameters involved in the formulation. It was shown that the sound pressure along the entire boundary of the rectangular enclosure can be accurately approximated without meshing. The same enclosure with an inner rigid acoustic screen is then used to reduce the sound pressure level within a chosen area through optimizing the shape of the screen, which shows the remarkable potentials of the proposed approach as a shape optimal tool for inner sound field problems.

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Numerical shape optimization of photoacoustic resonators

Cited by 31 publications

References 12 publications

A miniaturized prototype of resonant banana-shaped photoacoustic cell for gas sensing

A miniaturized prototype of resonant banana-shaped photoacoustic cell for gas sensing

Optimization and complete characterization of a photoacoustic gas detector

Shape Optimization of Acoustic Enclosures Based on a Wavelet–Galerkin Formulation

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