Agnes Maurel - Academia.edu (original) (raw)
Papers by Agnes Maurel
Physical Review E, 1996
We present an experimental study of a planar jet confined in a rectangular cavity. In certain geo... more We present an experimental study of a planar jet confined in a rectangular cavity. In certain geometrical configurations and for sufficiently large Reynolds numbers, this system exhibits self-sustained oscillations characterized by a well-defined wavelength and frequency of the jet. We describe flow regimes observed by varying the Reynolds number and the cavity length. The self-sustained oscillation regime is studied in detail: we extract the fundamental frequency and determine the selection criterion for the wavelength using a method of visualization, which has the advantage of being non intrusive. We show the existence of a band of allowed wavelengths and establish the upper and lower limits for the wavelength selection criterion. We discuss the validity of the visualization method for the measurement of the wavelength and frequency using a simple analytical model of the streaklines.
The Journal of the Acoustical Society of America, 2014
A multimodal method based on the admittance matrix is used to analyze wave propagation through sc... more A multimodal method based on the admittance matrix is used to analyze wave propagation through scatterers of arbitrary shape. Two cases are considered: a waveguide containing scatterers, and the scattering of a plane wave at oblique incidence to an infinite periodic row of scatterers. In both cases, the problem reduces to a system of two sets of first-order differential equations for the modal components of the wavefield, similar to the system obtained in the rigorous coupled wave analysis. The system can be solved numerically using the admittance matrix, which leads to a stable numerical method, the basic properties of which are discussed (convergence, reciprocity, energy conservation). Alternatively, the admittance matrix can be used to get analytical results in the weak scattering approximation. This is done using the plane wave approximation, leading to a generalized version of the Webster equation and using a perturbative method to analyze the Wood anomalies and Fano resonances. V
The Journal of the Acoustical Society of America, 2004
The scattering amplitude for the scattering of anti-plane shear waves by screw dislocations, and ... more The scattering amplitude for the scattering of anti-plane shear waves by screw dislocations, and of in-plane shear and acoustic waves by edge dislocations are computed within the framework of elasticity theory. The former case reproduces well-known results obtained on the basis of an electromagnetic analogy. The latter case involves four scattering amplitudes in order to fully take into account mode conversion, and an adequately generalized optical theorem for vector waves is provided. In contrast to what happens for scattering by obstacles, the scattering amplitude increases with wavelength, and, in general, mode conversion in the forward direction does not vanish.
The Journal of the Acoustical Society of America, 2007
The attenuation of ultrasound in polycrystalline materials is modeled with grain boundaries consi... more The attenuation of ultrasound in polycrystalline materials is modeled with grain boundaries considered as arrays of dislocation segments, a model valid for low angle mismatches. The polycrystal is thus studied as a continuous medium containing many dislocation "walls" of finite size randomly placed and oriented. Wave attenuation is blamed on the scattering by such objects, an effect that is studied using a multiple scattering formalism. This scattering also renormalizes the speed of sound, an effect that is also calculated. At low frequencies, meaning wavelengths that are long compared to grain boundary size, then attenuation is found to scale with frequency following a law that is a linear combination of quadratic and quartic terms, in agreement with the results of recent experiments performed in copper ͓Zhang et al., J. Acoust. Soc. Am. 116͑1͒, 109-116 ͑2004͔͒. The prefactor of the quartic term can be obtained with reasonable values for the material under study, without adjustable parameters. The prefactor of the quadratic term can be fit assuming that the drag on the dynamics of the dislocations making up the wall is one to two orders of magnitude smaller than the value usually accepted for isolated dislocations. The quartic contribution is compared with the effect of the changes in the elastic constants from grain to grain that is usually considered as the source of attenuation in polycrystals. A complete model should include this scattering as well.
![Research paper thumbnail of Erratum: Propagation of guided waves through weak penetrable scatterers [J. Acoust. Soc. Am. 131(3), 1874–1889 (2012)]](https://attachments.academia-assets.com/88538797/thumbnails/1.jpg)
](The Journal of the Acoustical Society of America, 2012
The Journal of the Acoustical Society of America, 1999
A new experiment of a filamentary vortex in water characterized by ultrasound is presented. The f... more A new experiment of a filamentary vortex in water characterized by ultrasound is presented. The flow is generated by two corotating discs in an infinite medium, and suction can be applied at the center of the discs. Acoustic time reversal mirrors [see Roux et al., ASA Proc. 1433 (1998)] provide dynamical, nonintrusive, and global measurements of the vortex characteristics. Three different regimes are observed depending on the control parameters (distance between the discs, rotation frequency of the discs, and suction flow rate): (1) a regime of stable, stationary vortex where the velocity profile is compared to the Burgers model and scaling laws are investigated when varying the control parameters, (2) a regime of intermittency with cycles of vortex breakdowns, and (3) a domain where the vortex never shows up.
The Journal of the Acoustical Society of America, 2012
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
Journal of Applied Physics, 2009
The properties of prismatic dislocation loops, generated by radiation in metals, have remained el... more The properties of prismatic dislocation loops, generated by radiation in metals, have remained elusive for decades, and recent advances in computational capabilities as well as transmission electron microscopy have renewed interest in their study. Acoustic and elastic waves could become an interesting, nonintrusive, probe to this end, as they have for other dislocation configurations. What then are the characteristics of elastic wave scattering that would be sensitive to a prismatic loop signature? In this paper, we report the scattering cross section for an elastic wave by a prismatic dislocation loop. It differs in significant ways from the analog quantity in the case of pinned dislocation segments, the most significant being the polarization of the scattered wave. The properties of a coherent wave traveling through an elastic medium filled with randomly placed and randomly oriented such loops are also reported. At long wavelengths, the effective wave velocity and attenuation coefficients resemble those for a similar case with pinned dislocation segments.
Physical Review E, 1996
We present an experimental study of a planar jet confined in a rectangular cavity. In certain geo... more We present an experimental study of a planar jet confined in a rectangular cavity. In certain geometrical configurations and for sufficiently large Reynolds numbers, this system exhibits self-sustained oscillations characterized by a well-defined wavelength and frequency of the jet. We describe flow regimes observed by varying the Reynolds number and the cavity length. The self-sustained oscillation regime is studied in detail: we extract the fundamental frequency and determine the selection criterion for the wavelength using a method of visualization, which has the advantage of being non intrusive. We show the existence of a band of allowed wavelengths and establish the upper and lower limits for the wavelength selection criterion. We discuss the validity of the visualization method for the measurement of the wavelength and frequency using a simple analytical model of the streaklines.
The Journal of the Acoustical Society of America, 2014
A multimodal method based on the admittance matrix is used to analyze wave propagation through sc... more A multimodal method based on the admittance matrix is used to analyze wave propagation through scatterers of arbitrary shape. Two cases are considered: a waveguide containing scatterers, and the scattering of a plane wave at oblique incidence to an infinite periodic row of scatterers. In both cases, the problem reduces to a system of two sets of first-order differential equations for the modal components of the wavefield, similar to the system obtained in the rigorous coupled wave analysis. The system can be solved numerically using the admittance matrix, which leads to a stable numerical method, the basic properties of which are discussed (convergence, reciprocity, energy conservation). Alternatively, the admittance matrix can be used to get analytical results in the weak scattering approximation. This is done using the plane wave approximation, leading to a generalized version of the Webster equation and using a perturbative method to analyze the Wood anomalies and Fano resonances. V
The Journal of the Acoustical Society of America, 2004
The scattering amplitude for the scattering of anti-plane shear waves by screw dislocations, and ... more The scattering amplitude for the scattering of anti-plane shear waves by screw dislocations, and of in-plane shear and acoustic waves by edge dislocations are computed within the framework of elasticity theory. The former case reproduces well-known results obtained on the basis of an electromagnetic analogy. The latter case involves four scattering amplitudes in order to fully take into account mode conversion, and an adequately generalized optical theorem for vector waves is provided. In contrast to what happens for scattering by obstacles, the scattering amplitude increases with wavelength, and, in general, mode conversion in the forward direction does not vanish.
The Journal of the Acoustical Society of America, 2007
The attenuation of ultrasound in polycrystalline materials is modeled with grain boundaries consi... more The attenuation of ultrasound in polycrystalline materials is modeled with grain boundaries considered as arrays of dislocation segments, a model valid for low angle mismatches. The polycrystal is thus studied as a continuous medium containing many dislocation "walls" of finite size randomly placed and oriented. Wave attenuation is blamed on the scattering by such objects, an effect that is studied using a multiple scattering formalism. This scattering also renormalizes the speed of sound, an effect that is also calculated. At low frequencies, meaning wavelengths that are long compared to grain boundary size, then attenuation is found to scale with frequency following a law that is a linear combination of quadratic and quartic terms, in agreement with the results of recent experiments performed in copper ͓Zhang et al., J. Acoust. Soc. Am. 116͑1͒, 109-116 ͑2004͔͒. The prefactor of the quartic term can be obtained with reasonable values for the material under study, without adjustable parameters. The prefactor of the quadratic term can be fit assuming that the drag on the dynamics of the dislocations making up the wall is one to two orders of magnitude smaller than the value usually accepted for isolated dislocations. The quartic contribution is compared with the effect of the changes in the elastic constants from grain to grain that is usually considered as the source of attenuation in polycrystals. A complete model should include this scattering as well.
The Journal of the Acoustical Society of America, 2012
The Journal of the Acoustical Society of America, 1999
A new experiment of a filamentary vortex in water characterized by ultrasound is presented. The f... more A new experiment of a filamentary vortex in water characterized by ultrasound is presented. The flow is generated by two corotating discs in an infinite medium, and suction can be applied at the center of the discs. Acoustic time reversal mirrors [see Roux et al., ASA Proc. 1433 (1998)] provide dynamical, nonintrusive, and global measurements of the vortex characteristics. Three different regimes are observed depending on the control parameters (distance between the discs, rotation frequency of the discs, and suction flow rate): (1) a regime of stable, stationary vortex where the velocity profile is compared to the Burgers model and scaling laws are investigated when varying the control parameters, (2) a regime of intermittency with cycles of vortex breakdowns, and (3) a domain where the vortex never shows up.
The Journal of the Acoustical Society of America, 2012
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
Journal of Applied Physics, 2009
The properties of prismatic dislocation loops, generated by radiation in metals, have remained el... more The properties of prismatic dislocation loops, generated by radiation in metals, have remained elusive for decades, and recent advances in computational capabilities as well as transmission electron microscopy have renewed interest in their study. Acoustic and elastic waves could become an interesting, nonintrusive, probe to this end, as they have for other dislocation configurations. What then are the characteristics of elastic wave scattering that would be sensitive to a prismatic loop signature? In this paper, we report the scattering cross section for an elastic wave by a prismatic dislocation loop. It differs in significant ways from the analog quantity in the case of pinned dislocation segments, the most significant being the polarization of the scattered wave. The properties of a coherent wave traveling through an elastic medium filled with randomly placed and randomly oriented such loops are also reported. At long wavelengths, the effective wave velocity and attenuation coefficients resemble those for a similar case with pinned dislocation segments.