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Gotowa bibliografia na temat „Pressure-Wave-Propagation method”

Autor: Grafiati

Data publikacji: 21 grudnia 2024

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Artykuły w czasopismach na temat "Pressure-Wave-Propagation method"

HoIe, S. "Recent developments in the pressure wave propagation method". IEEE Electrical Insulation Magazine 25, nr 3 (maj 2009): 7–20. http://dx.doi.org/10.1109/mei.2009.4976898.

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Miyazaki, Yusuke, Jon Farmer, Miki Morimatsu, Shota Ito, Séan Mitchell i Paul Sherratt. "Brain Pressure Wave Propagation during Baseball Impact". Proceedings 49, nr 1 (15.06.2020): 149. http://dx.doi.org/10.3390/proceedings2020049149.

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Tommasin, Caenen, Verhegghe, Greenwald i Segers. "Physics of Within-Tissue Wave Propagation Generated by Pulse Propagation in the Carotid Artery". Applied Sciences 9, nr 14 (18.07.2019): 2878. http://dx.doi.org/10.3390/app9142878.

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(1) Background: We aimed to assess the validity of laser Doppler vibrometry (LDV) as an emerging method to measure the local pulse wave velocity (PWV) from skin displacement generated by the pressure pulse inside an underlying artery. (2) Methods: A finite element model representing a simplified common carotid artery embedded within a soft tissue mimicking material was used to reproduce how tissue motions due to a wave propagation along the artery radiates to the skin surface. A parametric study was set up, varying: (i) the pressure conditions inside the artery (shock and traveling pressure impulse), (ii) the arterial depth and (iii) the geometry in a patient-specific artery model. (3) Results: under all conditions, the arterial pulse induced primary and secondary waves at the skin surface; of which the propagation speed deviated from the imposed PWV (deviations between −5.0% to 47.0% for the primary wave front). (4) Conclusions: the propagation of a short pressure impulse induced complex skin displacement patterns revealing a complicated link between PWV and measured propagation speeds at the skin surface. Wave propagation at the skin level may convey information about arterial PWV, however, advanced signal analysis techniques will be necessary to extract local PWV values.

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Zhang, Xiu Hua, i Yan Yan Wu. "Numerical Analysis of Shock Wave Propagation Law of Internal Gas Explosion". Applied Mechanics and Materials 105-107 (wrzesień 2011): 299–302. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.299.

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The purpose of this paper is to research on shock wave propagation law of internal gas explosion. The multi-material Eulerian and Lagrangian coupling algorithm was adopt. Using ANSYS/LS-DYNA dynamic analysis software to build frame structure, air and gas explosion models. Multiple ALE elements for simulating air and gas explosion material the analysis of blast shock wave propagation in a three-story steel frame structure and the characteristics of explosion pressure using fluid-structure coupling method are carried out. The conclusions show that fluid-structure coupling method can well simulated shock wave propagation of internal gas explosion, and the pressure peak of blast shock wave increased with the increasing of the blast air initial energy. Locality is the characteristic of explosion pressure in sealed space, and the pressure pass weakly when it propagates in solid.

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William-Louis, M. J. P., i C. Tournier. "Calculation of Pressure Wave Propagation Through a Tube Junction". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, nr 3 (maj 1996): 239–44. http://dx.doi.org/10.1243/pime_proc_1996_210_193_02.

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This paper describes a new method for the calculation of pressure wave propagation through a junction. The unsteady model, valid for subsonic flow, takes into account the fluid compressibility and pressure losses according to the type of junction. A new method called the ‘branch superposition method’ is used for the numerical calculation, and consists of uncoupling the system of governing equations. During the propagation of pressure waves through a three-tube junction, two branches are inlet or outlet. Therefore, to uncouple the system, one of the two branches with incoming flow is modelled as a source or one of the two branches with outgoing flow as a sink. This method, combined with the method of characteristics, gives the possibility of predicting the propagation of pressure waves through a junction, where the fluid may be initially at rest or not. The model is validated by a comparison with experimental results.

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Wei, Kang, Yuangui Mei, Qi Sun i Xiao Hu. "Propagation Characteristics of Initial Compression Wave Induced by 400 km/h High-Speed Trains Passing through Very Long Tunnels". Applied Sciences 14, nr 13 (8.07.2024): 5946. http://dx.doi.org/10.3390/app14135946.

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When high-speed trains enter tunnels, an initial compression wave is generated. As the compression wave propagates at the local speed of sound to the tunnel exit, it radiates into the surrounding environment, forming micro-pressure waves (MPWs). MPWs create sonic booms, resulting in significant environmental issues. The magnitude of the micro-pressure waves is directly proportional to the pressure gradient of the compression wave at the tunnel exit. The nonlinear effects of the initial compression wave during propagation lead to a significant increase in pressure gradient. Therefore, the propagation characteristics of the initial compression wave during the tunnel are the crucial factor affecting the amplitude of MPWs. Based on the one-dimensional compressible unsteady non-isentropic flow model and the improved generalized Riemann variable characteristic method, this paper researched the propagation and evolution characteristics of an initial compression wave generated when 400 km/h high-speed trains enter tunnels with three portal shapes: (no tunnel entrance hood (no hood), an oblique, enlarged tunnel entrance hood (type A), an enlarged equal-section non-uniform opening hole tunnel entrance hood (type B)). The results show that when the initial compression wave propagates inside very long tunnels, the pressure gradient of the compression wave exhibits a trend of initially increasing and then decreasing with the increase in propagation distance. When the pressure gradient of the compression wave reaches its maximum value, the corresponding propagation distance is the steepening critical distance. For no tunnel entrance hoods, type A tunnel entrance hoods, and type B tunnel entrance hoods, the steepening critical distances are 5 km, 6 km, and 16 km, respectively. The steepening critical distance shortens with increasing train speed. Steady friction and unsteady friction effects mainly affect the pressure amplitude and pressure gradient during compression wave propagation, respectively. At lower ambient temperatures, the nonlinear effects in compression wave propagation are significantly enhanced. The mitigation effects of type A tunnel entrance hoods and type B tunnel entrance hoods on pressure gradient reduction are mainly concentrated within 4 km and 12 km, respectively. It is necessary to determine the optimal matching relationship between the tunnel entrance hood and tunnel length based on the characteristics of compression wave propagation to ensure their mitigating performance is maximized.

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Sun, Yali, Feihu Zheng, Zhenlian An, Yewen Zhang, Stephane Hole, Zhien Zhu, Liming Yang i in. "Pressure wave propagation method for space charge measurement in coaxial geometry". IEEE Transactions on Dielectrics and Electrical Insulation 25, nr 6 (grudzień 2018): 2139–46. http://dx.doi.org/10.1109/tdei.2018.007234.

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Yang, Jun, Junhua He, Dezhi Zhang, Haibin Xu, Guokai Shi, Min Zhang, Wenxiang Liu i Yang Zhang. "Local Phase-Amplitude Joint Correction for Free Surface Velocity of Hopkinson Pressure Bar". Applied Sciences 10, nr 15 (4.08.2020): 5390. http://dx.doi.org/10.3390/app10155390.

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The Hopkinson pressure bar is widely used to measure the reflected pressure of blast waves over a short distance. However, dispersion effects will occur when the elastic stress waves propagate in the pressure bar due to lateral inertia, and there will be errors between the signals obtained from the sensors and the actual loading. For the free surface velocity measured in our system, we developed a local phase-amplitude joint correction method to convert the measured velocity into the average reflected pressure of a shock wave at the impact end of the bar, considering factors such as propagation modes of the elastic wave, the frequency components’ time of arrival, velocity variation over the bar axis, and the stress–velocity relationship. Firstly, the Pochhammer–Chree frequency equation is calculated numerically, and the first to fourth orders of phase velocity, group velocity, normalized frequency, and propagation time curves of elastic wave propagation in 35CrMnSiA steel are obtained. Secondly, the phase and amplitude correction formulas for calculating average reflected pressure from center velocity are derived based on the propagation mode of the axial elastic wave in the pressure bar by analyzing the time-frequency combined spectrum obtained by short-time Fourier transform. Thirdly, a local phase-amplitude joint correction algorithm based on propagation mode is proposed in detail. The experimental tests and data analyses are carried out for eight sets of pressure bar. The results show that this method can identify the propagation mode of elastic waves in the bar intuitively and clearly. The first three orders of propagation modes are stimulated in the bar 04, while only the first order of propagation is stimulated in the other eight bars. The local phase-amplitude joint correction algorithm can avoid correcting the component of the non-axial elastic wave. The rising edge of the average stress curve on the impact surface of bar 01 and bar 04 is corrected from 4.13 μs and 4.09 μs to 2.70 μs, respectively.

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Akkas, N., i F. Erdogan. "The Residual Variable Method Applied to Acoustic Wave Propagation from a Spherical Surface". Journal of Vibration and Acoustics 115, nr 1 (1.01.1993): 75–80. http://dx.doi.org/10.1115/1.2930318.

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The classical wave equation in spherical coordinates is expressed in terms of a residual potential applying the Residual Variable Method. This method essentially eliminates the second derivative of the potential with respect to the radial coordinate from the wave equation. Thus, the dynamic pressure distribution on the surface of a spherical cavity can be studied by considering the cavity surface only. Moreover, the Residual Variable Method, being amenable to “marching” solutions in a finite-difference implementation, is very suitable for the analysis of acoustic wave propagation into the finite medium from the cavity surface. The propagation of the wave from the internal surface can be followed numerically. There is no need to discretize the infinite domain in its entirety at all. The propagation analysis can be terminated at any point in the radial direction without having to consider the rest.

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Shatalova, N., T. Apasov, Al Shatalov i B. Grigoriev. "Renovation method of restoring well productivity using wavefields". Journal of Mining Institute 258 (30.12.2022): 986–97. http://dx.doi.org/10.31897/pmi.2022.108.

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A stagewise theoretical substantiation of the renovation vibrowave method of influencing the near-wellbore zone of reservoir for restoring well productivity is presented. The area of treatment by the proposed method covers the reservoir with a heterogeneous permeability with fractures formed by fracking. In this method a decrease in concentration of colmatants occurs due to a change in direction of contaminants migration. Under the influence of pressure pulses, they move deep into the reservoir and disperse through the proppant pack. The results of mathematical modelling of the propagation of pressure wave and velocity wave and the calculations of particles entrainment in wave motion are presented.

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Rozprawy doktorskie na temat "Pressure-Wave-Propagation method"

Gunasekaran, Barani. "Development and validation of a pressure based CFD methodology for acoustic wave propagation and damping". Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8740.

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Combustion instabilities (thermo-acoustic pressure oscillations) have been recognised for some time as a problem limiting the development of low emissions (e.g., lean burn) gas turbine combustion systems, particularly for aviation propulsion applications. Recently, significant research efforts have been focused on acoustic damping for suppression of combustion instability. Most of this work has either been experimental or based on linear acoustic theory. The last 3-5 years has seen application of density based CFD methods to this problem, but no attempts to use pressure-based CFD methods which are much more commonly used in combustion predictions. The goal of the present work is therefore to develop a pressure-based CFD algorithm in order to predict accurately acoustic propagation and acoustic damping processes, as relevant to gas turbine combustors. The developed computational algorithm described in this thesis is based on the classical pressure-correction approach, which was modified to allow fluid density variation as a function of pressure in order to simulate acoustic phenomena, which are fundamentally compressible in nature. The fact that the overall flow Mach number of relevance was likely to be low ( mildly compressible flow) also influenced the chosen methodology. For accurate capture of acoustic wave propagation at minimum grid resolution and avoiding excessive numerical smearing/dispersion, a fifth order accurate Weighted Essentially Non-Oscillatory scheme (WENO) was introduced. Characteristic-based boundary conditions were incorporated to enable accurate representation of acoustic excitation (e.g. via a loudspeaker or siren) as well as enable precise evaluation of acoustic reflection and transmission coefficients. The new methodology was first validated against simple (1D and 2D) but well proven test cases for wave propagation and demonstrated low numerical diffusion/dispersion. The proper incorporation of Characteristic-based boundary conditions was validated by comparison against classical linear acoustic analysis of acoustic and entropy waves in quasi-1D variable area duct flows. The developed method was then applied to the prediction of experimental measurements of the acoustic absorption coefficient for a single round orifice flow. Excellent agreement with experimental data was obtained in both linear and non-linear regimes. Analysis of predicted flow fields both with and without bias flow showed that non-linear acoustic behavior occurred when flow reversal begins inside the orifice. Finally, the method was applied to study acoustic excitation of combustor external aerodynamics using a pre-diffuser/dump diffuser geometry previously studied experimentally at Loughborough University and showed the significance of boundary conditions and shear layer instability to produce a sustained pressure fluctuation in the external aerodynamics.

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William-Louis, Mame Jean Pierre. "Etude aérothermodynamique de la propagation des ondes de pression lors de la circulation des trains en tunnels simples ou ramifiés". Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/8a9bc601-5e51-4f33-9b4d-97889ee8f87e.

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Lorsqu'un train circule dans un tunnel, de fortes fluctuations de pression sont générées et se propagent sous forme d'ondes. L'écoulement généré dans ces conditions est turbulent, instationnaire et l'air peut devenir compressible. Dans le but de simuler la propagation des ondes, nous avons mené une étude théorique en supposant que les ondes sont planes, et qu'on a un écoulement par tranche. Ainsi, un modèle non homentropique, base sur les équations unidimensionnelles de la dynamique des gaz, a été construit, puis résolu par la méthode des caractéristiques. Ce modèle prend en compte la présence de jonction de tubes, permettant ainsi d'étudier le cas des tunnels ramifiés. Le code de calcul construit à partir de cette étude a permis de simuler la propagation des ondes dans des tunnels simples ou ramifiés, et de faire une étude paramétrique. Les résultats obtenus montrent que l'intensité des ondes dépend de la vitesse du train, du rapport de blocage, des formes du train et du tunnel. Le frottement favorise le pistonnement, tandis que la présence de jonction diminue cet effet et disperse les ondes.

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Zheng, Lin. "Étude et caractérisation des interfaces conducteur/isolant par la méthode de l'onde de pression". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS288.

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Les interfaces entre un conducteur et un isolant sont généralement supposées parfaites, c'est-à-dire que la longueur de Debye dans l'isolant est supposée très grande devant son épaisseur. Il est montré dans ce travail que ce n'est pas le cas et que des états d'interface produisent un potentiel de contact qui peut modifier grandement le comportement de l'interface lorsque le matériau est soumis à un champ électrique intense. En effet le dipôle d'interface à l'origine de la tension d'interface modifie la courbure des bandes d'énergie et donc favorise au au contraire contrarie l'injection ou l'extraction de charges. Une série d'expériences a été réalisée en utilisant la méthode d'onde de pression implémentée à l'aide d'un générateur acoustique de forte puissance sur des échantillons de polyéthylène de différents types, avec différentes électrodes et avec différentes conditions expérimentales. Les dipôles d'interface observés par la mesure influent effectivement sur l'injection de charges lorsque le matériau est sous haute tension. On peut remarquer que l'aluminium a une influence plus importante, notamment lorsqu'il est utilisé avec de l'huile silicone. Lorsque l'isolant ne possède pas d'électrodes, il est préférable de le coupler directement à un polymère chargé en carbone avec de l'huile silicone plutôt que de lui déposer des électrodes sous vide. Le dipôle d'interface observé est en effet plus proche de celui observé avec des électrodes en polymère chargé en carbone collées à chaud. Lors de la mise sous tension, on remarque que les charges pénètrent d'abord dans l'échantillon du fait du dipôle d'interface. La migration de ces charges produisent alors des injections secondaires dues à un effet de champ. La fluoration de la surface des échantillons n'a pas significativement amélioré la situation et n'opère donc pas comme un rempart aux charges, mais plutôt comme une barrière à la diffusion d'impuretés
The interfaces between a conductor and an insulator are generally assumed to be perfect, meaning that the Debye length in the insulator is considered to be much larger than its thickness. However, this work shows that this is not the case and that interface states generate a contact potential that can significantly alter the behavior of the interface when the material is subjected to a strong electric field. Indeed, the interface dipole responsible for the interface voltage modifies the curvature of the energy bands and thus either promotes or hinders charge injection or extraction. A series of experiments was conducted using the pressure wave method, implemented with a high-power acoustic generator on various polyethylene samples, with different electrodes and under various experimental conditions. The interface dipoles observed through measurement do indeed influence charge injection when the material is under high voltage. It is noteworthy that aluminum has a greater influence, particularly when used with silicone oil. When the insulator does not have electrodes, it is preferable to directly couple it with a carbon-filled polymer and silicone oil rather than deposit electrodes on it under vacuum. The interface dipole observed is indeed closer to that seen with carbon-filled polymer electrodes hot-bonded to the material. Upon applying voltage, charges initially penetrate the sample due to the interface dipole. The migration of these charges then leads to secondary injections caused by a field effect. Fluorinating the surface of the samples did not significantly improve the situation and thus does not act as a shield against charges, but rather as a barrier to the diffusion of impurities

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Widehammar, Svante. "A Method for Dispersive Split Hopkinson Pressure Bar Analysis Applied to High Strain Rate Testing of Spruce Wood". Doctoral thesis, Uppsala University, Department of Materials Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2872.

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En metod för dispersiv analys av försök med delad hopkinsonstång tillämpad på provning av granved vid hög töjningshastighet

Syftet var att etablera en metod för att studera sambandet mellan spänning och töjning för granved vid hög töjningshastighet. Detta åstadkoms genom att anpassa och något vidareutveckla tekniken med delad hopkinsonstång ("Split Hopkinson Pressure Bar", SHPB).

Vanligtvis har hopkinsonstavar cirkulärt tvärsnitt och en diameter som är mycket mindre än de verksamma våglängderna. Under sådana förhållanden är vågutbredningen i stängerna approximativt ickedispersiv, och en endimensionell (1D) vågutbredningsmodell kan användas. När det, som är fallet i denna studie, däremot inte kan säkerställas att stängernas tvärdimensioner är små i förhållande till våglängderna, är en helt igenom 1D vågutbredningsmodell otillräcklig, och tvärsnittets geometri, vilken var kvadratisk i denna studie, måste beaktas. Därför utvecklades med hjälp av Hamiltons princip en approximativ 3D vågutbredningsmodell för stänger med godtyckligt tvärsnitt. Modellen ger ett dispersionssamband (vågtal som funktion av vinkelfrekvens) samt medelvärden för förskjutningar och spänningar över gränsytorna mellan stänger och provstav. En kalibreringsprocedur utvecklades också.

Provning av granved genomfördes vid hög töjningshastighet (omkring 103 s-1) med den anpassade SHPB-tekniken, samt för jämförelse vid låg (8×10-3 s-1) och måttlig (17 s-1) töjningshastighet med en servohydraulisk provningsmaskin. Fukthalterna i veden motsvarade ugnstorr, fibermättnad och fullständig mättnad, och proven utfördes i radiell, tangentiell och axiell riktning i förhållande till trädets stam. För vart fall utfördes fem försök vid rumstemperatur. Resultaten visar töjningshastighetsberoendet för sambandet mellan spänning och töjning för granved under alla studerade förhållanden.

The aim was to establish a method for studying the relation between stress and strain in spruce wood at high strain rate. This was achieved by adapting and somewhat further developing the split Hopkinson pressure bar (SHPB) technique.

Hopkinson bars usually have a circular cross-section and a diameter much smaller than the operative wavelengths. The wave propagation in the bar is then approximately non-dispersive and a one-dimensional (1D) wave propagation model can be used. When, as in this study, it is not certain that the transverse dimensions of the bars are small in relation to the wavelengths, a solely 1D wave propagation model is insufficient and the geometry of the cross-section, which was square in this study, must be taken into account. Therefore, an approximate 3D wave propagation model for bars with arbitrary cross-section was developed using Hamilton's principle. The model provides a dispersion relation (wavenumber vs. angular frequency) and average values for displacements and stresses over the bar/specimen interfaces. A calibration procedure was also developed.

Tests on spruce wood specimens were carried out at a high strain rate (about 10³ s^-1) using the adapted SHPB technique, and for comparison at low (8×10^-3 s^-1) and medium (17 s^-1) strain rates using a servohydraulic testing machine. The moisture contents of the wood specimens corresponded to oven dry, fibre saturated and fully saturated, and the testing was performed in the radial, tangential and axial directions relative to the stem of the tree. In each case, five tests were run at room temperature. The results show the strain rate dependence of the relation between stress and strain for spruce wood under all conditions studied.

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Resch, Janelle. "Nonlinear Wave Propagation in Brass Instruments". Thesis, 2012. http://hdl.handle.net/10012/7282.

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The study of wave production and propagation is a common phenomenon seen within a variety of math and physics problems. This thesis in particular will investigate the production and propagation of sound waves through musical instruments. Although this field of work has been examined since the late 1800s, approaching these types of problems can be very difficult. With the exception of the last fifty years, we have only been able to approach such problems by linearizing the necessary equations of gas dynamics. Without the use of a computer, one can only get so far in studying nonlinear acoustic problems. In addition, the numerical theory for nonlinear problems is incomplete. Proving stability is challenging and there are a variety of open problems within this field. This thesis will be examining the propagation of sound waves specifically through brass instruments. However, we will not be able to fully examine this problem in a master’s thesis because of the complexity. Instead, the objective is to provide a foundation and global picture of this problem by merge the fields of nonlinear acoustics as well as computational and analytical gas dynamics. To study the general behaviour of nonlinear wave propagation (and to verify previous findings), experiments have been carried on a trumpet. The purpose of these experiments is take measurements of the sound pressure waves at various locations along the instrument in order to understand the evolution of the wave propagation. In particular, we want to establish if the nonlinear distortion is strong enough to have musical consequences; and if there are such outcomes, what prerequisites are required for the observable behaviour. Additionally, by using the discontinuous Galerkin numerical method, a model of the system will be presented in this thesis. It will then be compared with the experimental data to verify how well we were able to describe the nonlinear wave motion within a trumpet.

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Roach, Lisa Aretha Nyala. "Temporal Variations in the Compliance of Gas Hydrate Formations". Thesis, 2012. http://hdl.handle.net/1807/44081.

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Seafloor compliance is a non-intrusive geophysical method sensitive to the shear modulus of the sediments below the seafloor. A compliance analysis requires the computation of the frequency dependent transfer function between the vertical stress, produced at the seafloor by the ultra low frequency passive source-infra-gravity waves, and the resulting displacement, related to velocity through the frequency. The displacement of the ocean floor is dependent on the elastic structure of the sediments and the compliance function is tuned to different depths, i.e., a change in the elastic parameters at a given depth is sensed by the compliance function at a particular frequency. In a gas hydrate system, the magnitude of the stiffness is a measure of the quantity of gas hydrates present. Gas hydrates contain immense stores of greenhouse gases making them relevant to climate change science, and represent an important potential alternative source of energy. Bullseye Vent is a gas hydrate system located in an area that has been intensively studied for over 2 decades and research results suggest that this system is evolving over time. A partnership with NEPTUNE Canada allowed for the investigation of this possible evolution. This thesis describes a compliance experiment configured for NEPTUNE Canada’s seafloor observatory and its failure. It also describes the use of 203 days of simultaneously logged pressure and velocity time-series data, measured by a Scripps differential pressure gauge, and a Güralp CMG-1T broadband seismometer on NEPTUNE Canada’s seismic station, respectively, to evaluate variations in sediment stiffness near Bullseye. The evaluation resulted in a (- 4.49 x10-3± 3.52 x 10-3) % change of the transfer function of 3rd October, 2010 and represents a 2.88% decrease in the stiffness of the sediments over the period. This thesis also outlines a new algorithm for calculating the static compliance of isotropic layered sediments.

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Części książek na temat "Pressure-Wave-Propagation method"

O'Donovan, J., C. O'Sullivan i G. Marketos. "Micromechanics of Seismic Wave Propagation in Granular Materials". W Discrete Element Modelling of Particulate Media, 245–54. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00245.

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This paper uses Discrete Element Method (DEM) simulations in order to obtain insight into the wave propagation mechanism through a granular material. A three dimensional face-centred cubic sample system was subjected to an isotropic confining stress. A seismic wave was generated by translating a single particle, in a situation analogous to a laboratory bender element test. The propagation of the wave-induced disturbance through the system was visualised by using particle scale methods such as plotting individual particle velocities and representative particle shear stresses. It was possible to compare the current study with previous research in the literature to identify different wave components. Arrival of the wave was found by tracking the displacement of a single particle in the sample (the receiver in a bender element test). Different travel time determination techniques available in the literature were used in an attempt to calculate an arrival time for the shear wave component and thus the velocity of the shear wave. The shear wave velocity was used to calculate a value for the shear modulus of the medium. A parametric study illustrating the effect of confining pressure on the sample shear modulus was carried out and agreement was found with theoretical predictions in the literature, even though the best way of identifying the wave travel time remains elusive.

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Yang, Jing, Li-hong Gu, Kai Wang, Jiong Zhu, Ying-ying Zhao, Wei-feng Shi, Min Lin, Jian Yang i Wen-Rong Si. "Simulation Study on Ultrasonic Signal Propagation Characteristics of Partial Discharge in Transformers". W Advances in Transdisciplinary Engineering. IOS Press, 2024. http://dx.doi.org/10.3233/atde231268.

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Ultrasonic detection method is widely used to detect partial discharge (PD) in transformers because of its anti-electromagnetic interference and high sensitivity. It is of great significance to understand the sound wave propagation characteristics in transformers for ultrasonic signal detection and sensor arrangement optimization. In this paper, based on the finite element method, the ultrasonic signal propagation characteristics of PD in transformers are numerically studied, and the acoustic wave propagation characteristics in transformers are analyzed. The calculation results show the following facts: the multiple reflections of sound waves have a significant influence on the sound field distribution in transformers, and the sound pressure drops to 40Pa at 2500 μs; The absorption coefficient of the transformers has little influence on sound wave propagation, but when the absorption coefficient of the wall increases from 0.2 to 0.8, the pulse response time of receivers will be less than 1/2 of the original, and the arrival time difference in the area where the direct wave signal cannot be detected will be increased. When optimizing the sensor layout, priority should be given to the position with few obstacles, such as the area facing the winding gap.

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Timushev, Sergey, Andrey Aksenov i Jiawen Li. "Acoustic-Vortex Decomposition Method for CFD-CAA Study of Blade Machine Noise". W Vortex Dynamics - Theoretical, Experimental and Numerical Approaches [Working Title]. IntechOpen, 2024. http://dx.doi.org/10.5772/intechopen.1006111.

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This chapter presents a method for calculating the generation of pressure pulsations and noise emission by blade machines based on the decomposition of the compressible medium velocity field into vortex and acoustic modes. This method of acoustic-vortex decomposition of the basic equations of motion of a compressible medium leads to an inhomogeneous wave equation with respect to enthalpy pulsations, which includes pseudo-sonic oscillations in the source vortex region and acoustic oscillations in the near-field and far-field. The source function in the wave equation is determined from the independent solution of the vortex mode equations. The boundary conditions for the wave equation are formulated using complex specific acoustic impedance and pseudo-sonic oscillations. This method allows for the consideration of the influence of inhomogeneity and turbulence of the flow, rotor interference, sound diffraction on the elements of the flow part, and impedance characteristics of the machine surfaces, while ensuring the accuracy and speed of calculations. The acoustic-vortex method represents the noise source as a function of the vortex mode velocity field. This approach eliminates the arbitrariness and conventionality of the aeroacoustic analogy, defining the source, pressure pulsations, and noise propagation in the near-field as a direct result of numerical modelling.

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Yang, Jing, Kai Wang, Li-hong Gu, Hao-lu Hu, Yao-jun Zhou, Jia-yu Liu, An-feng Jiang, Jian Yang i Wen-rong Si. "Research on Partial Discharge Localization Method of Transformer Based on the Simulated Annealing Algorithm". W Advances in Transdisciplinary Engineering. IOS Press, 2024. http://dx.doi.org/10.3233/atde231267.

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Accurate localization of partial discharge (PD) in a transformer can help find the insulation fault of the transformer in time and avoid more serious power accidents. Due to the influence of the transformer box and internal structure, the measured value may deviate from the real value, resulting in a large error in the localization result of the Time Difference of Arrival (TDOA) method. In this paper, a sound pressure-distance localization model based on intensity is proposed, and the model is solved by the simulated annealing algorithm. The calculation results show that the simulated annealing algorithm can effectively avoid the objective function from falling into the local optimal solution, and the localization accuracy is within 10 cm when the measured value is accurate enough. Due to the scalar property of sound pressure and the attenuation characteristics of ultrasonic waves, the direct wave can be detected by optimizing sensor arrangement, and the influence of sound wave propagation in solid and refraction and reflection can be eliminated. This paper provides a new solution for PD localization and detection of transformers.

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Djojodihardjo, Harijono. "Acoustic Method for the Suppression of Acoustic and Aerodynamically Induced Vibration on Structures". W Modeling and Simulation Techniques in Structural Engineering, 1–37. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-0588-4.ch001.

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The close relationship between noise and vibration is reviewed and analyzed for the suppression of noise and vibration in structures. The suppression of noise and vibration by acoustic means are addressed. For the first, an analysis is carried out by representing noise by monopoles and higher harmonics, and to devise a straight-forward method to counter their influence by selective secondary acoustic source. The second problem is analyzed using a methodology developed earlier for the computational scheme for the calculation of the acoustic disturbance to the aeroelasticity of structures. The generic approach of the latter consists of three parts. The first is the formulation of the acoustic wave propagation governed by the Helmholtz equation by using boundary element approach, to allow the calculation of the acoustic pressure on the acoustic-structure boundaries. The structural dynamic problem is formulated using finite elements. The third part involves the calculation of the unsteady aerodynamics loading on the structure using generic unsteady aerodynamics computational method.

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Glass, Irvine I., i J. P. Sislian. "Transition Fronts". W Nonstationary Flows and Shock Waves, 19–45. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198593881.003.0003.

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Abstract The various shock-wave phenomena described in the previous section involve considerable spatial and time-dependent changes in velocity, density, pressure, and temperature in the continuum in which they take place and, therefore, they may be studied by the methods of nonstationary gas dynamics. The propagation of plane waves, and of cylindrical waves, or spherical waves in a duct with variable cross section is a special case of wave propagation. The analysis may be greatly simplified by the assumption of one-dimensional flow, whereby the flow properties are assumed to be uniform over any cross section and to vary only with the distance along the duct axis and also with time. However, in a real gas viscosity will cause a departure from this uniformity. Consequently, the onedimensional representation of real flows requires the use of appropriately defined average flow quantities at each cross section. In what follows, it will be assumed that the dynamic and thermodynamic variables describing the flow in the ducts are suitably averaged over a cross section and that they are functions of distance, r (along the duct axis), and time only.

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Streszczenia konferencji na temat "Pressure-Wave-Propagation method"

Haque, N., S. Dalai, S. Chakravorti i B. Chatterjee. "Space charge measurement in dielectrics using Pressure Wave Propagation method". W 2015 International Conference on Condition Assessment Techniques in Electrical Systems (CATCON). IEEE, 2015. http://dx.doi.org/10.1109/catcon.2015.7449540.

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Haque, Nasirul, Biswendu Chatterjee i Sivaji Chakravorti. "Simulation of pressure wave propagation method for space charge measurement in dielectrics". W 2015 International Conference on Energy, Power and Environment: Towards Sustainable Growth (ICEPE). IEEE, 2015. http://dx.doi.org/10.1109/epetsg.2015.7510111.

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Salame, Basil, i Stephane Hole. "The pressure wave propagation method for the study of interface electric field". W 2015 IEEE Electrical Insulation Conference. IEEE, 2015. http://dx.doi.org/10.1109/icacact.2014.7223595.

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Cheng, Lin, Lisheng Zhong, Yue Zhang i Jingliang Chen. "Study on electrical properties of cell suspension by the pressure wave propagation method". W 2010 10th IEEE International Conference on Solid Dielectrics (ICSD). IEEE, 2010. http://dx.doi.org/10.1109/icsd.2010.5568008.

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Satoh, Y. "Observation of charge behavior in organic photoconductor using the pulsed electroacoustic method and pressure wave propagation method". W Seventh International Conference on Dielectric Materials, Measurements and Applications. IEE, 1996. http://dx.doi.org/10.1049/cp:19961003.

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Fukuyoshi, F., D. Gotoh, Y. Tanaka, T. Takada, R. Watanabe, N. Tomita i R. Liu. "Observation of charge accumulation process in electron beam irradiated polymers using pressure wave propagation method". W Proceedings of 2005 International Symposium on Electrical Insulating Materials, 2005. (ISEIM 2005). IEEE, 2005. http://dx.doi.org/10.1109/iseim.2005.193554.

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Ndour, Assane, Stephane Hole, Paul Leblanc i Thierry Paillat. "Direct observation of charge effects at liquid-solid interface with the pressure-wave-propagation method". W 2020 IEEE 3rd International Conference on Dielectrics (ICD). IEEE, 2020. http://dx.doi.org/10.1109/icd46958.2020.9341861.

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Haque, Nasirul, Biswendu Chatterjee i Sivaji Chakravorti. "Modeling of a piezoelectric transducer for application in space charge detection using pressure wave propagation method". W 2015 International Conference on Energy Economics and Environment (ICEEE). IEEE, 2015. http://dx.doi.org/10.1109/energyeconomics.2015.7235093.

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Yali Sun, Yewen Zhang, Stephane Hole, Peng Ma, Feihu Zheng i Zhenlian An. "Physical model of measuring space charge distribution by Pressure Wave Propagation method for high voltage cable". W 2016 International Conference on Condition Monitoring and Diagnosis (CMD). IEEE, 2016. http://dx.doi.org/10.1109/cmd.2016.7757832.

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Sato, Keiichi, Youhei Wada, Yoshitaka Noto i Yasuhiro Sugimoto. "Reentrant Motion in Cloud Cavitation due to Cloud Collapse and Pressure Wave Propagation". W ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30350.

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It is well known that reentrant jet motion in periodic cloud cavitation means upward flow from the cavity closure area of cloud cavitation. However the mechanism of reentrant motion seems to remain unsolved clearly. In the present study some experiments were conducted about the mechanism of reentrant motion in a fixed type cavity for a convergent-divergent nozzle. High speed video observation and image analysis based on the frame difference method were made about unsteady cloud cavitation with a periodic structure of cavitation cloud shedding. As a result, the main points are experimentally found as follows; 1) a typical pattern of reentrant motions can be caused by the pressure wave propagation from the collapse of cavitation cloud shed downstream and 2) the frame difference method is very useful in an image analysis for high speed video observation of cavitating flow because the trajectory of pressure waves can be clearly visualized by the method.

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Raporty organizacyjne na temat "Pressure-Wave-Propagation method"

Hart, Carl R., i Gregory W. Lyons. A Measurement System for the Study of Nonlinear Propagation Through Arrays of Scatterers. Engineer Research and Development Center (U.S.), listopad 2020. http://dx.doi.org/10.21079/11681/38621.

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Various experimental challenges exist in measuring the spatial and temporal field of a nonlinear acoustic pulse propagating through an array of scatterers. Probe interference and undesirable high-frequency response plague typical approaches with acoustic microphones, which are also limited to resolving the pressure field at a single position. Measurements made with optical methods do not have such drawbacks, and schlieren measurements are particularly well suited to measuring both the spatial and temporal evolution of nonlinear pulse propagation in an array of scatterers. Herein, a measurement system is described based on a z-type schlieren setup, which is suitable for measuring axisymmetric phenomena and visualizing weak shock propagation. In order to reduce directivity and initiate nearly spherically-symmetric propagation, laser induced breakdown serves as the source for the nonlinear pulse. A key component of the schlieren system is a standard schliere, which allows quantitative schlieren measurements to be performed. Sizing of the standard schliere is aided by generating estimates of the expected light refraction from the nonlinear pulse, by way of the forward Abel transform. Finally, considerations for experimental sequencing, image capture, and a reconfigurable rod array designed to minimize spurious wave interactions are specified. 15.

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