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Literatura académica sobre el tema "Acoustical vortices"

Autor: Grafiati

Publicado: 15 de marzo de 2025

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Artículos de revistas sobre el tema "Acoustical vortices"

Baudoin, M. y J. L. Thomas. "Acoustic Tweezers for Particle and Fluid Micromanipulation". Annual Review of Fluid Mechanics 52, n.º 1 (5 de enero de 2020): 205–34. http://dx.doi.org/10.1146/annurev-fluid-010719-060154.

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Acoustic tweezers powerfully enable the contactless collective or selective manipulation of microscopic objects. Trapping is achieved without pretagging, with forces several orders of magnitude larger than optical tweezers at the same input power, limiting spurious heating and enabling damage-free displacement and orientation of biological samples. In addition, the availability of acoustical coherent sources from kilo- to gigahertz frequencies enables the manipulation of a wide spectrum of particle sizes. After an introduction of the key physical concepts behind fluid and particle manipulation with acoustic radiation pressure and acoustic streaming, we highlight the emergence of specific wave fields, called acoustical vortices, as a means to manipulate particles selectively and in three dimensions with one-sided tweezers. These acoustic vortices can also be used to generate hydrodynamic vortices whose topology is controlled by the topology of the wave. We conclude with an outlook on the field's future directions.

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Gao, Lu, Haixiang Zheng, Qingyu Ma, Juan Tu y Dong Zhang. "Linear phase distribution of acoustical vortices". Journal of Applied Physics 116, n.º 2 (14 de julio de 2014): 024905. http://dx.doi.org/10.1063/1.4889860.

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Baudoin, Michael, Jean-Claude Gerbedoen, Antoine Riaud, Olivier Bou Matar, Nikolay Smagin y Jean-Louis Thomas. "Folding a focalized acoustical vortex on a flat holographic transducer: Miniaturized selective acoustical tweezers". Science Advances 5, n.º 4 (abril de 2019): eaav1967. http://dx.doi.org/10.1126/sciadv.aav1967.

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Acoustical tweezers based on focalized acoustical vortices hold the promise of precise contactless manipulation of millimeter down to submicrometer particles, microorganisms, and cells with unprecedented combined selectivity and trapping force. Yet, the widespread dissemination of this technology has been hindered by severe limitations of current systems in terms of performance and/or miniaturization and integrability. Here, we unleash the potential of focalized acoustical vortices by developing the first flat, compact, paired single electrode focalized acoustical tweezers. These tweezers rely on spiraling transducers obtained by folding a spherical acoustical vortex on a flat piezoelectric substrate. We demonstrate the ability of these tweezers to grab and displace micrometric objects in a standard microfluidic environment with unique selectivity. The simplicity of this system and its scalability to higher frequencies open tremendous perspectives in microbiology, microrobotics, and microscopy.

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Tay, Daniel y Ning Xiang. "Experimental study of instantaneous sound intensities in rectangular enclosures". Journal of the Acoustical Society of America 153, n.º 3_supplement (1 de marzo de 2023): A23. http://dx.doi.org/10.1121/10.0018019.

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Instantaneous and time-averaged intensities are relevant field quantities in architectural acoustics investigations. Modeling of intensity flows in coupled volumes and the effect of absorptive material on its trajectory in reverberation chambers have been studied recently. This work focuses on vortical energy flows with a derivation of instantaneous intensity in enclosed spaces and an experimental effort for investigating the changes over time in all field quantities of interest—instantaneous intensity, pressure, and velocity simultaneously. In this study, the scale modeling technique is applied to investigate instantaneous intensity flows experimentally measured using pressure-3D velocity sensors in a rectangular room. Experimental results suggest the presence of vortical intensity modes at specific frequencies correlated to the room dimensions. The resulting simulation of intensity vortices has potential applications in the acoustical design and analysis of complex room geometries where sound energy flows play a major role in the acoustics of the space such as that of coupled-volume spaces and small rooms for critical listening.

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Yang, Ling, Qingyu Ma, Juan Tu y Dong Zhang. "Phase-coded approach for controllable generation of acoustical vortices". Journal of Applied Physics 113, n.º 15 (21 de abril de 2013): 154904. http://dx.doi.org/10.1063/1.4801894.

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Zheng, Haixiang, Lu Gao, Qingyu Ma, Yafei Dai y Dong Zhang. "Pressure distribution based optimization of phase-coded acoustical vortices". Journal of Applied Physics 115, n.º 8 (28 de febrero de 2014): 084909. http://dx.doi.org/10.1063/1.4867046.

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Gong, Zhixiong y Michael Baudoin. "Three-dimensional trapping and assembly with synchronized spherical acoustical vortices". Journal of the Acoustical Society of America 148, n.º 4 (octubre de 2020): 2784. http://dx.doi.org/10.1121/1.5147746.

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Brunet, Thomas, Jean-Louis Thomas, Régis Marchiano y François Coulouvrat. "Experimental investigation of 3D shock waves on nonlinear acoustical vortices". Physics Procedia 3, n.º 1 (enero de 2010): 905–11. http://dx.doi.org/10.1016/j.phpro.2010.01.116.

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Brunet, Thomas, Jean-Louis Thomas, Régis Marchiano y François Coulouvrat. "Experimental observation of azimuthal shock waves on nonlinear acoustical vortices". New Journal of Physics 11, n.º 1 (7 de enero de 2009): 013002. http://dx.doi.org/10.1088/1367-2630/11/1/013002.

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Volke-Sepúlveda, K., A. O. Santillán y R. R. Boullosa. "Transfer of Angular Momentum to Matter from Acoustical Vortices in Free Space". Topologica 2, n.º 1 (2009): 016. http://dx.doi.org/10.3731/topologica.2.016.

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Más fuentes

Tesis sobre el tema "Acoustical vortices"

Almohamad, Samir. "Micro-manipulation de fluides miscibles et de fibres de collagène à l'aide de pinces acoustiques à faisceau unique". Electronic Thesis or Diss., Université de Lille (2022-....), 2024. http://www.theses.fr/2024ULILN038.

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Les techniques à ultrasons se sont révélées être des outils puissants pour contrôler les gouttelettes dispersées immiscibles. En modelant soigneusement le champ acoustique, ces gouttelettes peuvent être triées, divisées, fusionnées, ciblées sélectivement et repositionnées avec précision. Les méthodes courantes incluent l'utilisation d'ondes stationnaires pour capturer les gouttelettes à des nœuds ou des ventres de pression spécifiques, ainsi que l'emploi d'ondes progressives pour déplacer les gouttelettes le long du chemin de propagation de l'onde. Des percées récentes ont conduit au développement de pinces acoustiques sélectives, qui utilisent des faisceaux focalisés ou des vortex acoustiques pour la manipulation précise de gouttelettes individuelles. Cependant, la manipulation par ultrasons s'est traditionnellement concentrée sur les fluides immiscibles. Karlsen, Augustsson, et Bruus [Phys. Rev. Lett. 117, 114504 2016] ont suggéré la possibilité de manipuler des fluides miscibles avec des pinces sélectives. Cependant, leurs travaux étaient purement théoriques et aucune démonstration expérimentale n'a encore été réalisée. Une telle démonstration est complexe en raison du faible contraste acoustique entre les fluides miscibles et du processus de diffusion qui brouille progressivement l'interface.Cette recherche doctorale démontre expérimentalement la possibilité de structurer, de piéger et de déplacer des fluides miscibles à l'aide de pinces acoustiques sélectives. Elle explore les interactions complexes entre les ondes ultrasonores et les fluides miscibles, en se concentrant particulièrement sur les effets acoustiques non linéaires tels que la force de radiation acoustique et le streaming acoustique, ainsi que leur influence sur le comportement des fluides à des échelles microscopiques. L'installation expérimentale intègre des pinces acoustiques à faisceau unique avec des dispositifs microfluidiques, permettant un contrôle et une manipulation précis des fluides. Les résultats expérimentaux sont comparés à des simulations numériques, révélant une bonne concordance entre les deux.Nous avons également exploré la manipulation d'autres objets avec un faible contraste acoustique : les fibres de collagène. Nos résultats préliminaires suggèrent la possibilité de manipuler ces fibres dans un milieu fluide. Cette méthode non invasive présente un potentiel d'applications en ingénierie tissulaire et en recherche biomédicale
Ultrasound techniques have proven to be powerful tools for controlling dispersed immiscible droplets. By carefully shaping the acoustic field, these droplets can be sorted, divided, merged, selectively targeted, and repositioned with precision. Common methods include using standing waves to capture droplets at specific pressure nodes or antinodes, as well as employing traveling waves to move droplets along the path of wave propagation. Recent breakthroughs have led to the development of selective acoustic tweezers, which utilize focused beams or acoustic vortices for the precise manipulation of individual droplets. However, ultrasound-based manipulation has traditionally focused on immiscible fluids. Karlsen, Augustsson, and Bruus [Phys. Rev. Lett. 117, 114504 2016] suggested the possibility of manipulating miscible fluids with selective tweezers. However, their work was purely theoretical and no experimental demonstrations have been achieved so far. Such a demonstration is very challenging because of the weak acoustic contrast between miscible fluids and the diffusion process, progressively blurring the interface.This Ph.D. research experimentally demonstrates the possibility of patterning, trapping, and dislocating high-concentration miscible-fluid blobs (Ficoll) within a lower-concentration medium (water) using selective acoustic tweezers. It delves into the complex interactions between ultrasound waves and miscible fluids, with a particular focus on nonlinear acoustic effects such as acoustic radiation force and acoustic streaming and their influence on fluid behavior at microscales. The experimental setup integrates single-beam acoustical tweezers with microfluidic devices, allowing precise control and manipulation of fluids. The experimental results are compared with numerical simulations, resulting in good agreement between the two.We further explored the manipulation of other objects with low acoustic contrast: collagen fibers. Our preliminary results suggest the possibility of manipulating these fibers within a fluid medium. This noninvasive method has potential implications in tissue engineering and biomedical research

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Li, Wenhua. "Flow/acoustics mechanisms in two- and three-dimensional wake vortices". Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/400.

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Legendre, César. "On the interactions of sound waves and vortices". Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209147.

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The effects of vortices on the propagation of acoustic waves are numerous, from simple convection effects to instabilities in the acoustic phenomena, including absorption,

reflection and refraction effects. This work focusses on the effects of mean flow

vorticity on the acoustic propagation. First, a theoretical background is presented

in chapters 2-5. This part contains: (i) the fluid dynamics and thermodynamics

relations; (ii) theories of sound generation by turbulent flows; and (iii) operators taken

from scientific literature to take into account the vorticity effects on acoustics. Later,

a family of scalar operators based on total enthalpy terms are derived to handle mean

vorticity effects of arbitrary flows in acoustics (chapter 6). Furthermore, analytical

solutions of Pridmore-Brown’s equation are featured considering exponential boundary

layers whose profile depend on the acoustic parameters of the problem (chapter 7).

Finally, an extension of Pridmore-Brown’s equation is formulated for predicting the

acoustic propagation over a locally-reacting liner in presence of a boundary layer of

linear velocity profile superimposed to a constant cross flow (chapter 8).

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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Berglund, Albin. "Evolution of Cavity Tip Vortices in High-Pressure Turbines". Thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329369.

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This degree project in applied physics studies the tip gap flows over the rotor blades of a high-pressure turbine. The rotor blade used in the study has an improved design that utilizes both a cavity tip and an uneven profiling to reduce turbine loss. The designed rotor blade is shown to admit a 21% lower leakage mass flow rate across the tip gap than a reference rotor blade with a flat tip. By studying the designed rotor blade using transient CFD, the flow field of the tip gap region has been studied through one blade passage. The flow field characteristics of particular interest are the leakage mass flow rate across the tip gap region, which is proportional to turbine loss, and the characteristic vortices that reside within the cavity tip. By using post-processing scripts, the leakage mass flow rate has been calculated for every time step across one blade passage, showing a strong time dependence. The characteristic vortices are found using two different vortex detection algorithms, and their respective vorticity magnitude is shown to depend on the leakage mass flow rate. The simulation shows that the vorticity magnitude is increasing above a threshold of leakage mass flow rate, and that it is decreasing under this threshold. This effect is shown to destabilize the leakage mass flow rate, increasing its amplitude over its period of one blade passage.

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MEN'SHOV, Igor y Yoshiaki NAKAMURA. "On Instability of Acoustic Waves Propagating in Stratified Vortical Flows". The Japan Society of Mechanical Engineers, 2002. http://hdl.handle.net/2237/9091.

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Davis, James Arthur. "Acoustic-vortical-combustion interaction in a solid fuel ramjet simulator". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/12947.

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Durand, Christopher. "Validation of a CAA Code for a Case of Vortical Gust-Stator Interaction". University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1481203960382465.

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Shahriari, Nima. "On stability and receptivity of boundary-layer flows". Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196878.

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This work is concerned with stability and receptivity analysis as well as studies on control of the laminar-turbulent transition in boundary-layer flows through direct numerical simulations. Various flow configurations are considered to address flow around straight and swept wings. The aim of this study is to contribute to a better understanding of stability characteristics and different means of transition control of such flows which are of great interest in aeronautical applications. Acoustic receptivity of flow over a finite-thickness flat plate with elliptic leading edge is considered. The objective is to compute receptivity coefficient defined as the relative amplitude of acoustic disturbances and TS wave. The existing results in the literature for this flow case plot a scattered image and are inconclusive. We have approached this problem in both compressible and incompressible frameworks and used high-order numerical methods. Our results have shown that the generally-accepted level of acoustic receptivity coefficient for this flow case is one order of magnitude too high. The continuous increase of computational power has enabled us to perform global stability analysis of three-dimensional boundary layers. A swept flat plate of FSC type boundary layer with surface roughness is considered. The aim is to determine the critical roughness height for which the flow becomes turbulent. Global stability characteristics of this flow have been addressed and sensitivity of such analysis to domain size and numerical parameters have been discussed. The last flow configuration studied here is infinite swept-wing flow. Two numerical set ups are considered which conform to wind-tunnel experiments where passive control of crossflow instabilities is investigated. Robustness of distributed roughness elements in the presence of acoustic waves have been studied. Moreover, ring-type plasma actuators are employed as virtual roughness elements to delay laminar-turbulent transition.

QC 20161124

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Brynjell-Rahkola, Mattias. "Studies on instability and optimal forcing of incompressible flows". Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-218172.

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This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. The two boundary layer flows are studied through spectral element simulations and eigenvalue computations, which enable their long-term behavior as well as the mechanisms causing transition to be determined. The emergence of transition in these cases is found to originate from a linear flow instability, but whereas the onset of this instability in the Blasius flow can be associated with a localized region in the vicinity of the suction orifice, the instability in the Falkner–Skan–Cooke flow involves the entire flow field. Due to this difference, the results of the eigenvalue analysis in the former case are found to be robust with respect to numerical parameters and domain size, whereas the results in the latter case exhibit an extreme sensitivity that prevents domain independent critical parameters from being determined. The instability of the two helices is primarily addressed through experiments and analytic theory. It is shown that the well known pairing instability of neighboring vortex filaments is responsible for transition, and careful measurements enable growth rates of the instabilities to be obtained that are in close agreement with theoretical predictions. Using the experimental baseflow data, a successful attempt is subsequently also made to reproduce this experiment numerically. In the second part of the thesis, a novel method for computing the optimal forcing of a dynamical system is developed. The method is based on an application of the inverse power method preconditioned by the Laplace preconditioner to the direct and adjoint resolvent operators. The method is analyzed for the Ginzburg–Landau equation and afterwards the Navier–Stokes equations, where it is implemented in the spectral element method and validated on the two-dimensional lid-driven cavity flow and the flow around a cylinder.

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da, Cunha Daise Nunes Queiroz. "Properties of Flow Through the Ascending Aorta in Boxer Dogs with Mild Aortic Stenosis: Momentum, Energy, Reynolds Number, Womersley’s, Unsteadiness Parameter, Vortex Shedding, and Transfer Function of Oscillations from Aorta to Thoracic Wall". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243910694.

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Libros sobre el tema "Acoustical vortices"

Jackson, Thomas L. Role of acoustics in flame/vortex interactions. Hampton, Va: Institute for Computer Applications in Science and Engineering, 1993.

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Hoad, Danny R. Helicopter blade-vortex interaction locations - scale-model acoustics and free-wake analysis results. Hampton, Va: Langley Research Center, 1987.

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Krause, E. IUTAM Symposium on Dynamics of Slender Vortices: Proceedings of the IUTAM Symposium held in Aachen, Germany, 31 August - 3 September 1997. Dordrecht: Springer Netherlands, 1998.

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Raman, Ganesh. Enhanced mixing of an axisymmetric jet by aerodynamic excitation. Cleveland, Ohio: Lewis Research Center, 1986.

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Raman, Ganesh. Enhanced mixing of an axisymmetric jet by aerodynamic excitation. Cleveland, Ohio: Lewis Research Center, 1986.

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Capítulos de libros sobre el tema "Acoustical vortices"

Tsuji, Kinko. "Acoustic Spirals: Analysis of Bach’s Prelude in C Major". En Spirals and Vortices, 113–25. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05798-5_5.

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Tsuji, Kinko. "Correction to: Acoustic Spirals: Analysis of Bach’s Prelude in C Major". En Spirals and Vortices, C1. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-05798-5_17.

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Inoue, O. y Y. Hattori. "Acoustic Sound Generated by Collision of Two Vortex Rings". En IUTAM Symposium on Dynamics of Slender Vortices, 361–68. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5042-2_30.

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Baffico, Maurizio, Denis Boyer y Fernando Lund. "Multiple Scattering of Acoustic Waves by Many Slender Vortices". En IUTAM Symposium on Dynamics of Slender Vortices, 379–87. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5042-2_32.

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Shchurov, Vladimir A. "Vortices of Acoustic Intensity Vector in the Shallow Water Waveguide". En Movement of Acoustic Energy in the Ocean, 77–118. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1300-6_4.

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Makita, H. y T. Hasegawa. "Acoustic Control of Vortical Structure in a Plane Jet". En Eddy Structure Identification in Free Turbulent Shear Flows, 77–88. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2098-2_8.

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Kerschen, E. J. "Receptivity of Boundary Layers to Acoustic and Vortical Free-Stream Disturbances". En Advances in Soil Science, 239–49. New York, NY: Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3430-2_30.

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Kerschen, E. J., M. Choudhari y R. A. Heinrich. "Generation of Boundary Layer Instability Waves by Acoustic and Vortical Free-Stream Disturbances". En Laminar-Turbulent Transition, 477–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-84103-3_43.

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Yoshikawa, Shigeru. "Vortices on Sound Generation and Dissipation in Musical Flue Instruments". En Vortex Dynamics Theories and Applications. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.91258.

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Musical flue instruments such as the pipe organ and flute mainly consist of the acoustic pipe resonance and the jet impinging against the pipe edge. The edge tone is used to be considered as the energy source coupling to the pipe resonance. However, jet-drive models describing the complex jet/pipe interaction were proposed in the late 1960s. Such models were more developed and then improved to the discrete-vortex model and vortex-layer model by introducing fluid-dynamical viewpoint, particularly vortex sound theory on acoustic energy generation and dissipation. Generally, the discrete-vortex model is well applied to thick jets, while the jet-drive model and the vortex-layer model are valid to thin jets used in most flue instruments. The acoustically induced vortex (acoustic vortex) is observed near the amplitude saturation with the aid of flow visualization and is regarded as the final sound dissipation agent. On the other hand, vortex layers consisting of very small vortices along both sides of the jet are visualized by the phase-locked PIV and considered to generate the acceleration unbalance between both vortex layers that induces the jet wavy motion coupled with the pipe resonance. Vortices from the jet visualized by direct numerical simulations are briefly discussed.

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Rout, Siddharth. "Early Advancements in Turbulence-Generated Noise Modelling: A Review". En Boundary Layer Flows - Advances in Modelling and Simulation [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1002433.

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Turbulent flows generate a broadband of acoustic noise, which can be extremely important. So, there is need for modelling the generation and propagation of acoustic energy in fluid flows, especially turbulent. This chapter reviews the research work conducted to identify and quantify the noise field generated in turbulent flows. The story starts with the journey of experimental identification and measurement of noise generated from vortices. Various analytical models there were developed, soon after, the popularity of turbulence generated is discussed. The base path-breaking research on quantifying noise generation from conservation laws including Navier–stokes equations is discussed and further used for approximation of acoustic intensity by acoustic analogy with electrostatic quadrupole near-field and far-field. With the development of computational numerical techniques flow field for complex geometries and higher fidelity became possible. The candidates for relevant computational methods are touched and integration with turbulent models is discussed. Finally, a case of simulation of noise generation for turbulent flow over airfoil using acoustic equations and Reynolds-averaged Navier-Stokes (RANS) turbulent model is reviewed.

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Actas de conferencias sobre el tema "Acoustical vortices"

Haixiang Zheng, Yuzhi Li, Qingyu Ma y Dong Zhang. "Controllable generation of acoustical vortices with sparse sources". En 2015 IEEE International Ultrasonics Symposium (IUS). IEEE, 2015. http://dx.doi.org/10.1109/ultsym.2015.0448.

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Marchiano, Régis, Jean-Louis Thomas, Bengt Enflo, Claes M. Hedberg y Leif Kari. "Effects of the parametric interaction on the toplogical charge of acoustical vortices." En NONLINEAR ACOUSTICS - FUNDAMENTALS AND APPLICATIONS: 18th International Symposium on Nonlinear Acoustics - ISNA 18. AIP, 2008. http://dx.doi.org/10.1063/1.2956165.

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Marchiano, R. "Theoretical and experimental study of the topological charge of linear and nonlinear acoustical vortices". En INNOVATIONS IN NONLINEAR ACOUSTICS: ISNA17 - 17th International Symposium on Nonlinear Acoustics including the International Sonic Boom Forum. AIP, 2006. http://dx.doi.org/10.1063/1.2210391.

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Yamade, Yoshinobu, Chisachi Kato, Akiyoshi Iida, Shinobu Yoshimura y Keiichiro Iida. "Prediction of Pressure Fluctuation on a Vehicle by Large Eddy Simulation". En ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-17519.

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The objective of this study is to predict accurately interior aeroacoustics noise of a car for a wide range of frequency between 100 Hz and 4 kHz. One-way coupled simulations of computational fluid dynamics (CFD), structural analysis and acoustical analysis were performed to predict interior aeroacoustics noise. We predicted pressure fluctuations on the outer surfaces of a test car by computing unsteady flow around the car as the first step. Secondary, the predicted pressure fluctuations were fed to the subsequent structural analysis to predict vibration accelerations on the inner surfaces of the test car. Finally, acoustical analysis was performed to predict sound fields in the test car by giving vibration accelerations computed by the structural analysis as the boundary conditions. In this paper, we focus on the unsteady flow computations, which is the first step of the coupled simulations. Large Eddy Simulation (LES) was performed to predict the pressure fluctuations on the outer surfaces of the test car. We used the computational mesh composed of approximately 5 billion hexahedral grids with a spatial resolution of 1.5 mm in the streamwise and spanwise directions to resolve the dynamics of the small vortices in the turbulence boundary layer. Predicted and measured pressure fluctuation at several sampling points on the surface of the test car were compared and they matched well in a wide range of frequency up to 2 kHz.

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Li, Guoqiang y Ephraim J. Gutmark. "Geometry Effects on the Flow Field and the Spectral Characteristics of a Triple Annular Swirler". En ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38799.

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The dynamics of vortex breakdown are important to the performance of gas turbine combustors where swirling flows are extensively used to stabilize the flame and extend the lean flammability limit (LBO). Due to the strong interaction of vortical structures in the swirling flow with heat release and acoustical modes, vortex breakdown mechanism is essential to understanding the thermoacoustic behavior and to the development of combustion instability control strategy. This paper analyzes the vortex breakdown behavior downstream of a Triple Annular Research Swirler (TARS) based on velocity flow field data from stereoscopic PIV measurement and spectral data from hotwire/film measurements. The vortical structure is highly dependent on the different swirler combinations (swirler geometry) as well as on inlet conditions such as air flow-rate, mixing tube length and downstream conditions such as exhaust nozzle contraction ratio. The scale, location, strength, and formation mechanisms of the large-scale vortices vary for different geometries. The shape of the recirculation bubble changes with the outlet boundary conditions, suggesting that the swirling flow inside the combustion chamber remains subcritical downstream of the vortex breakdown. However, spectral analysis reveals that the dominant frequencies close to the exit of the TARS show only slight change for different outlet boundary conditions. Three ranges of frequencies characterize the spectral domain of TARS: high frequency close to the TARS exit, middle range frequency downstream of this region, and low frequency in most regions further downstream. The sources of instabilities in these three regions could be attributed to the strong shear layer, precessing vortex core and interaction between spanwise and azimuthal instabilities. The outlet boundary conditions affect the middle and low frequency range but have no effect on the high frequency. The inlet conditions have global effect on the entire flow region.

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Kannan, Ashwin y S. R. Chakravarthy. "A Framework to Predict Combustion Noise and Instability: Case Study of a Partially Premixed Flame in a Backward-Facing Step Combustor". En ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-65211.

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Incompressible large eddy simulations coupled with acoustics are performed to predict combustion noise and instability in a partially premixed based backward facing step combustor. The computational analysis adopts a simultaneous multi-scale spatio-temporal framework for flow and acoustics such that the flow/acoustics varies at a shorter/longer length scale and a longer/shorter time scale respectively. This engenders flow dilatation and acoustic Reynolds stress (ARS) as the external source terms in the acoustic energy and flow momentum respectively. Numerical results are presented for three cases, at a particular Reynolds number, wherein two of them constitute acoustically coupled (coupled long duct case) and its uncoupled counterpart (no acoustic feedback). The third corresponds to a shorter combustor length (coupled short duct case). These three cases contrast the strong acoustic feedback in the short duct case, both of which are compared with the acoustically uncoupled LES that is common to them. It is found that combustion occurs predominantly in the large-scale vortical structures in the coupled long duct case due to enhanced mixing between the reactants brought about by the strong acoustic feedback (ARS). Thus, the present work is able to not only distinguish between the flow and acoustic processes, but also handle both combustion noise and instability within the same framework.

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Harper, Chris, Chris Bibby, Nathan Hartford, Chase Harris y Cristian Popa. "Flow-Induced Vibration Assessment and Mitigation for Compressor Station Expansion". En 2024 15th International Pipeline Conference. American Society of Mechanical Engineers, 2024. https://doi.org/10.1115/ipc2024-133362.

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Abstract Compressor station expansion projects present a risk of fatigue failure due to flow-induced vibration. Flow-induced vibration mechanisms relevant to compressor stations include flow-induced turbulence, vortex-induced vibration on barred tees and thermowells, and flow-induced pulsations within deadlegs and strainers. Risk and severity of these vibration mechanisms increase with flow rate. Methodologies for assessing each are presented. The flow-induced turbulence mechanism is excitation due to turbulent kinetic energy in the flow. Screening assessment approach provided by the Energy Institute demonstrates that gas pipelines typically have low turbulent excitation provided the pipework is well supported. Barred (also called pigging or scraper) tees are commonly found in gas pipeline stations adjacent to pig barrels. They can be a vibration and failure risk due to flow-induced vibrations. Flow through the bars can create vortex shedding, similar to other bluff bodies in fluid flow, and excitation forces at the wake frequency. These forces can then excite the lateral modes of the bars. Common bar designs have several different bar lengths, each with their own natural frequency of vibration. This range of vibration frequencies increases the chance of resonance where a vortex shedding frequency coincides with a natural frequency of a bar. Other complicating factors are the non-uniform flow profile as the flow goes from the main header into the branch and the non-symmetrical shape of the bars that have a radius on the header side. Flow-induced pulsations from deadlegs occur when the vortex shedding frequency across a branch opening coincides with an acoustical natural frequency of the deadleg. These pulsations create shaking forces which can lead to high vibration and risk of fatigue failure. Vibration is amplified if the pulsation frequency coincides with a mechanical natural frequency of the pipework. A methodology is presented for identifying deadleg pulsation and assessing the resulting vibratory stress in the piping system. Inline cone strainers can generate very high-amplitude high-frequency vibration and noise local to the tee. Fatigue failure can occur. Strainer noise and vibration is known to occur when vortices are shed through the strainer holes at a frequency that coincides with acoustical cross modes in the pipe. This is further amplified if the acoustic mode coincides with a mechanical shell mode in the pipe wall. Both vibration and noise field data will be presented for the above mechanisms with techniques for identifying and evaluating risk during operation. Simple solutions will be given for reducing the risk of fatigue failure.

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CHAWLA, KALPANA y CHUEN-YEN CHOW. "Acoustic control of vortices". En 12th Aeroacoustic Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-1042.

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Naugolnykh, Konstantin. "Acoustic instability of vortices". En ICA 2013 Montreal. ASA, 2013. http://dx.doi.org/10.1121/1.4800704.

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Li, Wenhua, Z. C. Zheng y Ying Xu. "Flow/Acoustic Mechanisms in Three-Dimensional Vortices Undergoing Sinusoidal-Wave Instabilities". En ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43163.

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It has been identified that vorticity in a vortex core directly relates to the frequency of a significant sound peak from an aircraft wake vortex pair where each of the vortices is modeled as an elliptic core Kirchhoff vortex. In three-dimensional vortices, sinusoidal instabilities at various length scales result in significant flow structure changes in these vortices, and thus influence their radiated acoustic signals. In this study, a three-dimensional vortex particle method is used to simulate the incompressible vortical flow. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula that enables computation of acoustic signals radiated from an approximated incompressible flow field. Cases of vortex rings and a pair of counter-rotating vortices are studied when they are undergoing both long- and short-wave instabilities. Both inviscid and viscous interactions are considered and effects of turbulence are simulated using sub-grid-scale models.

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