Journal articles on the topic 'Propagative waves'
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1
Sheng, Xi, Huike Zeng, Sara Ying Zhang, and Ping Wang. "Numerical Study on Propagative Waves in a Periodically Supported Rail Using Periodic Structure Theory." Journal of Advanced Transportation 2021 (October 14, 2021): 1–12. http://dx.doi.org/10.1155/2021/6635198.
Abstract:
This paper presents the numerical study on propagative waves in a periodically supported rail below 6000 Hz. A periodic rail model, which considers the effects of both the periodic supports and the rail cross section deformation, has been established based on the periodic structure theory and the finite element method. Two selection approaches are proposed to obtain the concerned dispersion curves from the original calculation results of dispersion relations. The differences between the dispersion curves of different support conditions are studied. The propagative waves corresponding to the dispersion curves are identified by the wave modes. The influences of periodic supports on wave modes in pass bands are revealed. Further, the stop band behaviors are investigated in terms of the bounding frequencies, the standing wave characteristics, and the cross-sectional modes. The results show that eight propagative waves with distinct modes exist in a periodically supported rail below 6000 Hz. The differences between the dispersion curves of periodically and continuously supported rails are not obvious, apart from the stop band behaviors. All the bounding-frequency modes of the stop bands are associated with the standing waves. Two bounding-frequency modes of the same stop band can be regarded as two identical standing waves with the longitudinal translation of the quarter-wavelength, one of which is the so-called pinned-pinned resonance.
2
Dupuy, Bastien, Louis De Barros, Stephane Garambois, and Jean Virieux. "Wave propagation in heterogeneous porous media formulated in the frequency-space domain using a discontinuous Galerkin method." GEOPHYSICS 76, no. 4 (July 2011): N13—N28. http://dx.doi.org/10.1190/1.3581361.
Abstract:
Biphasic media with a dynamic interaction between fluid and solid phases must be taken into account to accurately describe seismic wave amplitudes in subsurface and reservoir geophysical applications. Consequently, the modeling of the wave propagation in heteregeneous porous media, which includes the frequency-dependent phenomena of the fluid-solid interaction, is considered for 2D geometries. From the Biot-Gassmann theory, we have deduced the discrete linear system in the frequency domain for a discontinuous finite-element method, known as the nodal discontinuous Galerkin method. Solving this system in the frequency domain allows accurate modeling of the Biot wave in the diffusive/propagative regimes, enhancing the importance of frequency effects. Because we had to consider finite numerical models, we implemented perfectly matched layer techniques. We found that waves are efficiently absorbed at the model boundaries, and that the discretization of the medium should follow the same rules as in the elastodynamic case, that is, 10 grids per minimum wavelength for a P0 interpolation order. The grid spreading of the sources, which could be stresses or forces applied on either the solid phase or the fluid phase, did not show any additional difficulties compared to the elastic problem. For a flat interface separating two media, we compared the numerical solution and a semianalytic solution obtained by a reflectivity method in the three regimes where the Biot wave is propagative, diffusive/propagative, and diffusive. In all cases, fluid-solid interactions were reconstructed accurately, proving that attenuation and dispersion of the waves were correctly accounted for. In addition to this validation in layered media, we have explored the capacities of modeling complex wave propagation in a laterally heterogeneous porous medium related to steam injection in a sand reservoir and the seismic response associated to a fluid substitution.
3
Smith, William V. "Wave motion in a conducting fluid with a layer adjacent to the boundary, II. Eigenfunction expansions." ANZIAM Journal 43, no. 2 (October 2001): 195–236. http://dx.doi.org/10.1017/s1446181100013031.
Abstract:
AbstractThe wave motion of magnetohydrodynamic (MHD) systems can be quite complicated. In order to study the motion of waves in a perfectly conducting fluid under the influence of an external magnetic field in a stratified medium, we make the simplifying assumption that the pressure is constant (to first order). This is the simplest form of the equations with variable coefficients and is not strongly propagative. Alfven waves are still present. The system is further simplified by assuming that the external field is parallel to the boundary. The Green's function for the operator is constructed and then the spectral family is constructed in terms of generalized eigenfunctions, giving four families of propagating waves, including waves “trapped” in the boundary layer. These trapped waves are interesting, since they are not the relics of surface waves, which do not exist in this context when the boundary layer shrinks to zero thickness no matter what (maximal energy preserving) boundary condition is chosen. We conjecture a similar structure for the full MHD problem.
4
Gavaix, Anne-Marie, Jean Chandezon, and Gerard Granet. "PROPAGATIVE AND EVANESCENT WAVES DIFFRACTED BY PERIODIC SURFACES: PERTURBATION METHOD." Progress In Electromagnetics Research B 34 (2011): 283–311. http://dx.doi.org/10.2528/pierb11070504.
5
Dupuy, Bastien, and Alexey Stovas. "Influence of frequency and saturation on AVO attributes for patchy saturated rocks." GEOPHYSICS 79, no. 1 (January 1, 2014): B19—B36. http://dx.doi.org/10.1190/geo2012-0518.1.
Abstract:
Partially saturated rocks are considered to be major sources of seismic wave velocity dispersion and attenuation in recorded real data. From the physical description of partially saturated gas-water and oil-water reservoirs, we use upscaling theories to compute an equivalent frequency-dependent porous medium. These homogenization methods are associated with mesoscale description of attenuation and dispersion coming from wave-induced flow phenomena. To compute wave propagation, we use numerical codes in the frequency domain that allow us to take into account all the frequency-dependent parameters without approximation or local time steps. In this way, the Biot slow compressional wave is well modeled and its partially diffusive, partially propagative behavior is completely considered. The attenuation and dispersion of the waves in such media are coming partly from the wave mode conversion into diffusive slow waves, not visible on seismograms. But the amplitude of propagative P- and S-waves are mainly affected by these energy losses at interfaces. Using full waveform modeling, we investigate the amplitude versus offset (AVO) attributes with respect to saturation and frequency. For a simple three-layer case, we compute poroelastic wave propagation, extract maximum amplitude with respect to angle, and, through a least-square fitting method, we obtain the AVO attributes for PP- and PS-reflected events. Due to the influence of mesoscale induced-flow phenomena and relatively to the regime of the Biot slow wave, the main results show a strong variability of the AVO attributes with the frequency and a lower variability with the saturation for reflected PP or PS events. We show that gas-water and oil-water systems have similar behaviors. Strong differences between patchy saturation and effective fluid phase theories are highlighted, especially at high frequency, for PP events and for gas-water systems. Then, we conclude that these AVO attributes carry information about the saturation that can be used to estimate the saturation variations in time-lapse studies.
6
Babilotte, Philippe. "Simulation of multiwavelength conditions in laser picosecond ultrasonics." SIMULATION 97, no. 7 (March 25, 2021): 473–84. http://dx.doi.org/10.1177/0037549721996451.
Abstract:
Complete numerical simulations are given under SciLab® and MATLAB® coding environments, concerning propagative acoustic wavefronts, for laser picosecond ultrasonics under multiwavelength conditions. Simulations of the deformation field and its propagation into bulk material are given under different wavelength configurations for optical pump and probe beams, which are used to generate and to detect the acoustic signal. Complete insights concerning the dynamics of the acoustic waves are given, considering the absence of carrier diffusions into the material. Several numerical approaches are proposed concerning both the functions introduced to simulate the wavefront ( Heaviside or error) and the coding approach (linear/vectorized/ Oriented Object Programming), under the pure thermo-elastic approach.
7
Intravaia, F., and A. Lambrecht. "The Role of Surface Plasmon Modes in the Casimir Effect." Open Systems & Information Dynamics 14, no. 02 (June 2007): 159–68. http://dx.doi.org/10.1007/s11080-007-9044-4.
Abstract:
In this paper, we study the role of surface plasmon modes in the Casimir effect. First we write the Casimir energy as the sum over the modes of a real cavity. We may identify two sorts of modes, two evanescent surface plasmon modes and propagative modes. As one of the surface plasmon modes becomes propagative for some choice of parameters we adopt an adiabatic mode definition where we follow this mode into the propagative sector and count it together with the surface plasmon contribution, calling this contribution “plasmonic”. The remaining modes are propagative cavity modes, which we call “photonic”. The Casimir energy contains two main contributions, one coming from the plasmonic, the other from the photonic modes. Surprisingly we find that the plasmonic contribution to the Casimir energy becomes repulsive for intermediate and large mirror separations. Alternatively, we discuss the common surface plasmon defintion, which includes only evanescent waves, where this effect is not found. We show that, in contrast to an intuitive expectation, for both definitions the Casimir energy is the sum of two very large contributions which nearly cancel each other. The contribution of surface plasmons to the Casimir energy plays a fundamental role not only at short but also at large distances.
8
ERMANYUK, E. V., J. B. FLÓR, and B. VOISIN. "Spatial structure of first and higher harmonic internal waves from a horizontally oscillating sphere." Journal of Fluid Mechanics 671 (February 10, 2011): 364–83. http://dx.doi.org/10.1017/s0022112010005719.
Abstract:
An experimental study is presented on the spatial structure of the internal wave field emitted by a horizontally oscillating sphere in a uniformly stratified fluid. The limits of linear theory and the nonlinear features of the waves are considered as functions of oscillation amplitude. Fourier decomposition is applied to separate first harmonic waves at the fundamental frequency and higher harmonic waves at multiples of this frequency. For low oscillation amplitude, of 10% of the sphere radius, only the first harmonic is significant and the agreement between linear theory and experiment is excellent. As the oscillation amplitude increases up to 30% of the radius, the first harmonic becomes slightly smaller than its linear theoretical prediction and the second and third harmonics become detectable. Two distinct cases emerge depending on the ratio Ω between the oscillation frequency and the buoyancy frequency. When Ω > 0.5, the second harmonic is evanescent and localized near the sphere in the plane through its centre perpendicular to the direction of oscillation, while the third harmonic is negligible. When Ω < 0.5, the second harmonic is propagative and appears to have an amplitude that exceeds the amplitude of the first harmonic, while the third harmonic is evanescent and localized near the sphere on either side of the plane through its centre perpendicular to the direction of oscillation. Moreover, the propagative first and second harmonics have radically different horizontal radiation patterns and are of dipole and quadrupole types, respectively.
9
Bristeau, Marie-Odile, Bernard Di Martino, Ange Mangeney, Jacques Sainte-Marie, and Fabien Souille. "Some quasi-analytical solutions for propagative waves in free surface Euler equations." Comptes Rendus. Mathématique 358, no. 11-12 (January 25, 2021): 1111–18. http://dx.doi.org/10.5802/crmath.63.
10
Gavrić, L. "Computation of propagative waves in free rail using a finite element technique." Journal of Sound and Vibration 185, no. 3 (August 1995): 531–43. http://dx.doi.org/10.1006/jsvi.1995.0398.
11
Jabiri, Ayoub, Abdelali Yacoubi, and Mhammed El Allami. "Plotting Lamb waves dispersion curves of an aluminum plate by the Semi-Analytical Finite Element (SAFE) method and comparison with analytical curves." ITM Web of Conferences 48 (2022): 02006. http://dx.doi.org/10.1051/itmconf/20224802006.
Abstract:
It is well known that the propagation of Lamb waves in elastic solid medias depends on the frequency and on the material properties, but it does not depend on the propagation direction in isotropic medias and gives rise to two basic types of modes, symmetric and antisymmetric ones. This paper presents an application of the semi-analytical finite element (SAFE) method on an isotropic aluminum plate of thickness e = 2mm. The main goal of this paper is to make a quantitative evaluation of the SAFE method by carrying out the following tasks: a) calculation of the dispersion curves (wavenumber, phase velocity, group velocity, b) calculation of the relative error and validation of the proposed algorithm, c) comparison between the curves obtained by SAFE method on those obtained by Bisection method. It should be noted here that our study is restricted on the propagative modes.
12
Bareille, O., and M. N. Ichchou. "Wave propagation in composite structures." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 3 (December 15, 2009): 639–48. http://dx.doi.org/10.1243/09544062jmes1971.
Abstract:
Dynamic behaviour of honeycomb-core composite structures forms the framework of this article. The wave numbers of propagative waves are the elements of comparison between a numerical method (wave finite-element method) and an experimental identification technique (inhomogeneous wave correlation). The numerical method is based on the description of the dynamics of periodic waveguides. The experimental technique uses a matching criterion with the measured displacement field to obtain the corresponding wave numbers for a wave-based description of the displacement. Both approaches are applied to a sandwich composite beam with a honeycomb core. They seem to be in quite good accordance with analytical results for the flexural wave number.
13
Nicolopoulos, Anouk, Martin Campos Pinto, Bruno Després, and Patrick Ciarlet. "Degenerate elliptic equations for resonant wave problems." IMA Journal of Applied Mathematics 85, no. 1 (February 2020): 132–59. http://dx.doi.org/10.1093/imamat/hxaa001.
Abstract:
Abstract The modelling of resonant waves in 2D plasma leads to the coupling of two degenerate elliptic equations with a smooth coefficient $\alpha $ and compact terms. The coefficient $\alpha $ changes sign. The region where $\{\alpha>0\}$ is propagative, and the region where $\{\alpha <0\}$ is non propagative and elliptic. The two models are coupled through the line $\varSigma =\{\alpha =0\}$. Generically, it is an ill-posed problem and additional information must be introduced to get a satisfactory treatment at $\varSigma $. In this work, we define the solution by relying on the limiting absorption principle ($\alpha $ is replaced by $\alpha +i0^+$) in an adapted functional setting. This setting lies on the decomposition of the solution in a regular and a singular part, which originates at $\varSigma $, and on quasi-solutions. It leads to a new well-posed mixed variational formulation with coupling. As we design explicit quasi-solutions, numerical experiments can be carried out, which illustrate the good properties of this new tool for numerical computation.
14
Elmaimouni, L., J. E. Lefebvre, F. E. Ratolojanahary, A. Raherison, B. Bahani, and T. Gryba. "Polynomial Approach Modeling of Resonator Piezoelectric Disc." Key Engineering Materials 482 (June 2011): 11–20. http://dx.doi.org/10.4028/www.scientific.net/kem.482.11.
Abstract:
Legendre polynomial method which describes the structure and incorporates automatically the boundary conditions in constitutive and propagation equations is used to model acoustic wave cylindrical resonators. It is the first time this method is applied to study standing rather than propagative waves. The advantage of this approach is, in a unique formulation, to take into account electric sources. The analytical and numerical resolutions are presented to highlight the potentialities of the Legendre polynomial approach. The vibration characteristics of piezoelectric discs with regard to diameter to thickness D/H ratios are analyzed by the three dimensional modeling approach through both modal and harmonic analyses. Resonance and antiresonance frequencies, electric input impedance, dispersion curves, field profiles and electromechanical coupling coefficient, easily obtained, are presented for PZT5A resonator piezoelectric discs. To validate our approach, the results using our 3D polynomial modelling of acoustic wave resonator are compared with those obtained by an approximated analytical method. The developed software proves to be very efficient to retrieve the radial modes of all orders.
15
Nissabouri, Salah, Moussa Mekkaoui, Hassan Rhimini, Mhammed El Allami, and Abdellah Zamma. "Semi-Analytical Finite Element Method for calculating dispersion curves of a CFRP plate." MATEC Web of Conferences 360 (2022): 00010. http://dx.doi.org/10.1051/matecconf/202236000010.
Abstract:
Composite Materials are widely used thanks to their mechanical characteristics. Non destructive evaluation requires knowing the exact dispersion curves to determine the propagative waves and to resolve the phase velocity of symmetrical and antisymmetrical modes. The aim of this paper is to plot the dispersion curves of a Carbon Fibre Reinforced Polymer plate using Semi Analytical Finite Element Method algorithm. This method combines the analytical expression of the displacement and the finite element method procedure. The resultant advantage is both simplicity and rapidity. The obtained results showed that the method accuracy depends on the elements number of meshing. To ensure good precision and fast computation of the method, the elements number and the order of the interpolation functions must be optimized.
16
Khelil, Khadidja, Azzeddine Dekhane, Aissa Benselhoub, and Stefano Bellucci. "Higher order dispersions effect on high-order soliton interactions." Technology audit and production reserves 2, no. 1(70) (April 28, 2023): 24–29. http://dx.doi.org/10.15587/2706-5448.2023.277346.
Abstract:
The object of the research is deleting the interaction of the higher order soliton interaction by introducing the third and fourth order dispersions inside an optical fiber. The results are obtained by the simulation of the nonlinear Schrödinger equation, which models the propagation of solitons in the optical fiber using the method of Fast Fourier Transform. The interaction of two higher order solitons due to the attraction of their electric field can lead to losing the solitons' properties. Hence, this can prevent the use of solitons in high-bit-rate optical fiber communication systems because it increases the bit error rate, significantly limiting the potential of the communication system. To resolve this problem, we should diminish the bit rate error by avoiding the interaction of the co-propagative solitons when they are too close. It is well known that, during higher order soliton propagation in the presence of the third order dispersion, the irregular shape of the higher order soliton disappears, and a splitting towards its fundamental constituents occurs after a considerable propagation. As for the fourth order, dispersion gives rise to two dispersive wave sidebands on the red or blue side. Our results reveal that bringing two higher order solitons together in the presence of the fourth order dispersion, a series of interactions between the components generated after their fission is obtained. In the third-order distribution, besides the fourth-order diffusion, the rare form and the supercontinuum generated by the fission of the higher-order solitons disappear, and we get two fundamental solitons propagating in parallel with a temporal shift and some inconsiderable dispersive waves. The most important aspect is that both higher-order dispersions are able to suppress the interactions of higher-order solitons thanks to the time shift induced by the third-order distribution and the intermittent compression caused by the fourth-order scattering. These results can be obtained in practice inside the dispersion-engineered photonic crystal waveguide (PhC-wg), which allows for manipulating the high order dispersion.
17
GUO, HAO, CANCAN WANG, PEIYUAN ZHANG, HONGJUN CHEN, YUN LI, LISHU WU, XIONG ZHANG, and YIPING CUI. "ENHANCED TRANSMITTANCE AND RESOLUTION OF PHOTONIC CRYSTAL FLAT LENS BY SURFACE-EDGE ENGINEERING." Modern Physics Letters B 26, no. 18 (June 17, 2012): 1250113. http://dx.doi.org/10.1142/s0217984912501138.
Abstract:
We proposed a novel two-dimensional (2D) photonic crystal (PC) flat lens based on the surface-edge engineering of a PC slab, operating as an n = -1 superlens at λ = 1.55 μm. The cross-section at the truncated edge of the flat lens is similar to an "anti-reflection grating", which is employed to reduce the reflectivity of propagative waves. The PC flat lens with a low reflectance of 1% was realized by the proposed truncated surface-edge for an InP / InGaAsP / InP 2D PC slab. The simulation results obtained with finite-difference time-domain (FDTD) method show that a PC flat super lens with a far-field resolution of 0.41 λ and a high transmittance of 81.9% can be achieved by the engineering of the truncated surface-edge at hetero-interface.
18
Hamabata, Hiromitsu, Tomikazu Namikawa, and Kazuhiro Mori. "The effect of lower-hybrid waves on the propagation of hydromagnetic waves." Journal of Plasma Physics 40, no. 2 (October 1988): 337–51. http://dx.doi.org/10.1017/s0022377800013313.
Abstract:
Propagation characteristics of hydromagnetic waves in a magnetic plasma are investigated using the two-plasma fluid equations including the effect of lower-hybrid waves propagating perpendicularly to the magnetic field. The effect of lower-hybrid waves on the propagation of hydromagnetic waves is analysed in terms of phase speed, growth rate, refractive index, polarization and the amplitude relation between the density perturbation and the magnetic-field perturbation for the cases when hydromagnetic waves propagate in the plane whose normal is perpendicular to both the magnetic field and the propagation direction of lower-hybrid waves and in the plane perpendicular to the propagation direction of lower-hybrid waves. It is shown that hydromagnetic waves propagating at small angles to the propagation direction of lower-hybrid waves can be excited by the effect of lower-hybrid waves and the energy of excited waves propagates nearly parallel to the propagation direction of lower-hybrid waves.
19
Dörnbrack, Andreas, Stephen D. Eckermann, Bifford P. Williams, and Julie Haggerty. "Stratospheric Gravity Waves Excited by a Propagating Rossby Wave Train—A DEEPWAVE Case Study." Journal of the Atmospheric Sciences 79, no. 2 (February 2022): 567–91. http://dx.doi.org/10.1175/jas-d-21-0057.1.
Abstract:
Abstract Stratospheric gravity waves observed during the DEEPWAVE research flight RF25 over the Southern Ocean are analyzed and compared with numerical weather prediction (NWP) model results. The quantitative agreement of the NWP model output and the tropospheric and lower-stratospheric observations is remarkable. The high-resolution NWP models are even able to reproduce qualitatively the observed upper-stratospheric gravity waves detected by an airborne Rayleigh lidar. The usage of high-resolution ERA5 data—partially capturing the long internal gravity waves—enabled a thorough interpretation of the particular event. Here, the observed and modeled gravity waves are excited by the stratospheric flow past a deep tropopause depression belonging to an eastward-propagating Rossby wave train. In the reference frame of the propagating Rossby wave, vertically propagating hydrostatic gravity waves appear stationary; in reality, of course, they are transient and propagate horizontally at the phase speed of the Rossby wave. The subsequent refraction of these transient gravity waves into the polar night jet explains their observed and modeled patchy stratospheric occurrence near 60°S. The combination of both unique airborne observations and high-resolution NWP output provides evidence for the one case investigated in this paper. As the excitation of such gravity waves persists during the quasi-linear propagation phase of the Rossby wave’s life cycle, a hypothesis is formulated that parts of the stratospheric gravity wave belt over the Southern Ocean might be generated by such Rossby wave trains propagating along the midlatitude waveguide.
20
Chauvin, Fabrice, Romain Roehrig, and Jean-Philippe Lafore. "Intraseasonal Variability of the Saharan Heat Low and Its Link with Midlatitudes." Journal of Climate 23, no. 10 (May 15, 2010): 2544–61. http://dx.doi.org/10.1175/2010jcli3093.1.
Abstract:
Abstract The Saharan heat low (SHL) is thought to be a key feature of the West African monsoon, and its variations during the summer season have not yet been systematically assessed. To characterize the intraseasonal variations of the SHL, real and complex empirical orthogonal function analyses were applied to the 850-hPa potential temperature field over northern Africa and the Mediterranean, using NCEP–Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) reanalysis results. A robust quasi-propagative mode was highlighted over North Africa and the Mediterranean. This mode consists of two phases. The west phase corresponds to a maximum temperature over the coast of Morocco–Mauritania, propagating southwestward, and a minimum between Libya and Sicily, propagating southeastward. The east phase corresponds to the opposite temperature structure, which propagates as in the west phase. A lag-composite analysis revealed that this SHL mode was preceded by large-scale, midlatitude, intraseasonal fluctuations of the atmosphere. The southward penetration of a Rossby wave disturbance over Europe and North Africa generates modulations of the three-dimensional atmospheric structure. The low-level ventilations and harmattan-like circulation are particularly impacted, as are the subtropical westerlies and the polar jets in the upper troposphere. The west phase is concomitant with an enhanced convective signal over the Darfur region, which propagates westward, as far as the middle of the Atlantic, at a speed similar to that of the well-known African easterly waves. The SHL appears to be a bridge between the midlatitudes and the West African monsoon, which may offer promising sources of predictability over the Sahel on an intraseasonal time scale.
21
Imamura, Takeshi. "Meridional Propagation of Planetary-Scale Waves in Vertical Shear: Implication for the Venus Atmosphere." Journal of the Atmospheric Sciences 63, no. 6 (June 1, 2006): 1623–36. http://dx.doi.org/10.1175/jas3684.1.
Abstract:
Abstract It is shown that planetary-scale waves are inherently accompanied by latitudinal momentum transport when they propagate vertically in vertically sheared zonal flows. Because of the dependence of the wave's latitudinal scale on the intrinsic phase speed, positive (negative) vertical shear should force prograde (retrograde) waves to focus equatorward and retrograde (prograde) waves to expand poleward in the course of upward propagation. Consequently, Eliassen–Palm (EP) flux vectors are tilted from the vertical and nonzero latitudinal momentum fluxes occur. The direction of momentum transport should always be equatorward (poleward) in positive (negative) vertical shear irrespective of the zonal propagation direction. The idea was applied to upwardly propagating waves in the Venusian middle atmosphere, where vertical shear of strong midlatitude jets and equatorial superrotation exist. Numerical solutions showed that Kelvin and prograde inertio-gravity waves focus equatorward and mixed Rossby–gravity and Rossby waves expand poleward below the cloud top. The former is attributed primarily to the vertical shear of the superrotation, while the latter to the vertical shear beneath the midlatitude jets. Such characteristics of planetary-scale waves will cause angular momentum separation between high and low latitudes and, at least partly, contribute to the maintenance of the superrotation.
22
Martini, Eduardo, André V. G. Cavalieri, and Peter Jordan. "Acoustic modes in jet and wake stability." Journal of Fluid Mechanics 867 (March 28, 2019): 804–34. http://dx.doi.org/10.1017/jfm.2019.148.
Abstract:
Motivated by recent studies that have revealed the existence of trapped acoustic waves in subsonic jets (Towne et al., J. Fluid Mech., vol. 825, 2017, pp. 1113–1152), we undertake a more general exploration of the physics associated with acoustic modes in jets and wakes, using a double vortex-sheet model. These acoustic modes are associated with eigenvalues of the vortex-sheet dispersion relation; they are discrete modes, guided by the vortex sheet; they may be either propagative or evanescent; and under certain conditions they behave in the manner of acoustic-duct modes. By analysing these modes we show how jets and wakes may both behave as waveguides under certain conditions, emulating ducts with soft or hard walls, with the vortex-sheet impedance providing effective ‘wall’ conditions. We consider, in particular, the role that upstream-travelling acoustic modes play in the dispersion-relation saddle points that underpin the onset of absolute instability. The analysis illustrates how departure from duct-like behaviour is a necessary condition for absolute instability, and this provides a new perspective on the stabilising and destabilising effects of reverse flow, temperature ratio and compressibility; it also clarifies the differing symmetries of jet (symmetric) and wake (antisymmetric) instabilities. An energy balance, based on the vortex-sheet impedance, is used to determine stability conditions for the acoustic modes: these may become unstable in supersonic flow due to an energy influx through the shear layers. Finally, we construct the impulse response of flows with zero and finite shear-layer thickness. This allows us to show how the long-time wavepacket behaviour is indeed determined by interaction between Kelvin–Helmholtz and acoustic modes.
23
Kanguzhin, Baltabek. "PROPAGATION OF NONSMOOTH WAVES UNDER SINGULAR PERTURBATIONS OF THE WAVE EQUATION." Eurasian Mathematical Journal 13, no. 3 (2022): 41–50. http://dx.doi.org/10.32523/2077-9879-2022-13-3-41-50.
24
Bian, Xu, Biwan Tian, and Shijiu Jin. "Finite element simulation study on influence of spacecraft stiffener structure on elastic wave propagation." MATEC Web of Conferences 336 (2021): 02002. http://dx.doi.org/10.1051/matecconf/202133602002.
Abstract:
Aiming at the propagation process of elastic wave in spacecraft stiffener structure. In this paper, the phase and energy changes of elastic waves propagating in the wall structure of stiffeners at different frequencies are analyzed by using finite element method and laser Doppler vibrometer (LDVS). Meanwhile, the relationship between the parameters of stiffeners and the diffusion of acoustic wave energy and the phase change of elastic waves respectively is obtained. The results show that in the range of parameters involved in this paper, the stiffener has a significant effect on elastic waves propagation. When wavelength λ > 10mm, most of the elastic waves are reflected by the stiffener, while when λ < 6mm, elastic waves propagate more easily across the stiffener, and the proportion of those propagated by the stiffener increases. Moreover, the functional expression of the relationship between the height of the stiffener and the frequency of the elastic wave which can easily propagate through the stiffener is obtained.
25
Martínez, Anxo, Alfredo Güemes, Jose M. Perales, and Jose M. Vega. "Variable Thickness in Plates—A Solution for SHM Based on the Topological Derivative." Sensors 20, no. 9 (April 29, 2020): 2529. http://dx.doi.org/10.3390/s20092529.
Abstract:
The topological derivative tool is applied here in structural health monitoring (SHM) problems to locate small defects in a material plate with complex geometry that is subject to permanent multifrequency guided waves excitation. Compared to more standard SHM methods, based in measuring the time-lag between emitted and received propagative pulses plus some postprocessing, the topological derivative somehow compares the measured and computed (solving the full elasto-dynamic equations) response of the damaged plate, instead of relying on only the time of flight of the wave. Thus, the method profits the knowledge behind the physics of the problem and can cope with scenarios in which classical methods give poor results. The authors of this paper have already used the topological derivative in rectangular plates with constant thickness, but with defects consisting simply in both through slits and inclusions of a different material, and actuators/sensors located near the boundary, which makes very difficult to use standard SHM methods. This is an extension of the method, also considering the much more difficult to analyze case of plates with variable thickness and complex (non-rectangular) planform.
26
Cai, Ming, Cory Barton, Chul-Su Shin, and Jeffrey M. Chagnon. "The Continuous Mutual Evolution of Equatorial Waves and the Quasi-Biennial Oscillation of Zonal Flow in the Equatorial Stratosphere*." Journal of the Atmospheric Sciences 71, no. 8 (July 23, 2014): 2878–85. http://dx.doi.org/10.1175/jas-d-14-0032.1.
Abstract:
Abstract The continuous mutual evolution of equatorial waves and the background quasi-biennial oscillation (QBO) is demonstrated using daily NCEP–U.S. Department of Energy (DOE) reanalysis for the period from 1 January 1979 to 31 December 2010. Using a novel diagnostic technique, the phase speed, vertical tilting, and form stress of equatorial waves in the stratosphere are obtained continuously on a daily basis. The results indicate that, on top of a weak-amplitude annual-cycle signal, all of these wave properties have a pronounced QBO signal with a downward propagation that evolves continuously together with the background QBO. The analysis also highlights the potential role of wave-induced form stress in driving the QBO regime change. Dominant waves in the equatorial stratosphere propagate very slowly relative to the ground at all times, implying that their observed intrinsic phase speed evolution follows the background QBO nearly exactly but with opposite sign, as the established theory predicts. By revealing the continuous evolution of the form stress associated with the vertically tilted waves, the new diagnostic method also demonstrates the dominance of eastward-tilted, eastward-propagating waves contributing to a deceleration of easterly flow at high altitudes, which causes a downward propagation of the easterly flow signal. Similarly, the dominance of westward-tilted, westward-propagating waves acts to reverse westerly flow to easterly flow and causes a downward propagation of westerly flow signal. The results suggest that in addition to the wave-breaking processes, such continuously alternating downward transfer of westerly and easterly angular momentum by westward-tilted, westward-propagating waves and eastward-tilted, eastward-propagating waves contributes to the wave–mean flow interaction mechanism for the QBO.
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Smirnov, Yury G., Eugenii Yu Smol’kin, and Dmitry V. Valovik. "Nonlinear Double-Layer Bragg Waveguide: Analytical and Numerical Approaches to Investigate Waveguiding Problem." Advances in Numerical Analysis 2014 (January 22, 2014): 1–11. http://dx.doi.org/10.1155/2014/231498.
Abstract:
The paper is concerned with propagation of surface TE waves in a circular nonhomogeneous two-layered dielectric waveguide filled with nonlinear medium. The problem is reduced to the analysis of a nonlinear integral equation with a kernel in the form of the Green function. The existence of propagating TE waves for chosen nonlinearity (the Kerr law) is proved using the contraction mapping method. Conditions under which k waves can propagate are obtained, and intervals of localization of the corresponding propagation constants are found. For numerical solution of the problem, a method based on solving an auxiliary Cauchy problem (the shooting method) is proposed. In numerical experiment, two types of nonlinearities are considered and compared: the Kerr nonlinearity and nonlinearity with saturation. New propagation regime is found.
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Shayakhmetov, S. B., Z. D. Kalpenova, K. S. Lesov, and Kh K. Umarov. "Rayleigh and love surface waves with regard to seismic stress state of earth bed." E3S Web of Conferences 401 (2023): 01077. http://dx.doi.org/10.1051/e3sconf/202340101077.
Abstract:
This article presents the results of studies on the propagation of surface seismic waves, which directly affect the stability and strength of a high embankment of the subgrade. The subgrade is the foundation of the railway track. In an elastic half-space with a layer in which surface waves propagate, the conditions for the existence and propagation of a harmonic Rayleigh wave are considered. The equations of motion of a medium in a layer and half-space and their solutions in the form of plane waves propagating in phase along the contact boundary, some general laws of Rayleigh wave propagation are given. The accepted theories and calculation methods' main provisions are proposed for designing a durable and reliable subgrade and considering its seismic stress state.
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Yang, Qiu, and Andrew J. Majda. "Upscale Impact of Mesoscale Disturbances of Tropical Convection on 2-Day Waves." Journal of the Atmospheric Sciences 76, no. 1 (January 1, 2019): 171–94. http://dx.doi.org/10.1175/jas-d-18-0049.1.
Abstract:
Abstract Westward-propagating 2-day waves with embedded mesoscale disturbances contribute a large portion of synoptic variability of tropical convection over the western Pacific. It is of crucial importance to assess the upscale impact on 2-day waves of these mesoscale disturbances that propagate at various tilt angles. Also, it will be informative to consider the upscale impact on both symmetric and asymmetric 2-day waves in terms of convection, morphology of circulation, and tropical cyclogenesis. A simple multiscale asymptotic model is used to simulate the two-scale structure of 2-day waves. The synoptic-scale circulation response is driven by westward-propagating mean heating and eddy transfer of momentum and temperature. The latter is interpreted as the upscale impact of mesoscale fluctuations. The upscale impact of mesoscale disturbances that propagate at a tilt angle between 315° and 45° induces low-level negative potential temperature anomalies and westerly inflow. Shallow congestus convection triggered in a moist environment at the leading edge of the 2-day waves supports the westward propagation. For asymmetric 2-day waves in the Northern Hemisphere, the upscale impact of mesoscale disturbances propagating at a tilt angle between 315° and 0° induces lower-tropospheric cyclonic flows and negative pressure perturbation. This provides a new mechanism to precondition tropical cyclogenesis. A comparison of the upscale impact on symmetric westward-propagating 2-day waves and eastward-propagating convectively coupled Kelvin waves shows that their tilt angle ranges with favorable conditions for convection and enhanced inflow are simply opposite.
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Palkar, Grishma, Jian-young Wu, and Bard Ermentrout. "The inhibitory control of traveling waves in cortical networks." PLOS Computational Biology 19, no. 9 (September 5, 2023): e1010697. http://dx.doi.org/10.1371/journal.pcbi.1010697.
Abstract:
Propagating waves of activity can be evoked and can occur spontaneously in vivo and in vitro in cerebral cortex. These waves are thought to be instrumental in the propagation of information across cortical regions and as a means to modulate the sensitivity of neurons to subsequent stimuli. In normal tissue, the waves are sparse and tightly controlled by inhibition and other negative feedback processes. However, alterations of this balance between excitation and inhibition can lead to pathological behavior such as seizure-type dynamics (with low inhibition) or failure to propagate (with high inhibition). We develop a spiking one-dimensional network of neurons to explore the reliability and control of evoked waves and compare this to a cortical slice preparation where the excitability can be pharmacologically manipulated. We show that the waves enhance sensitivity of the cortical network to stimuli in specific spatial and temporal ways. To gain further insight into the mechanisms of propagation and transitions to pathological behavior, we derive a mean-field model for the synaptic activity. We analyze the mean-field model and a piece-wise constant approximation of it and study the stability of the propagating waves as spatial and temporal properties of the inhibition are altered. We show that that the transition to seizure-like activity is gradual but that the loss of propagation is abrupt and can occur via either the loss of existence of the wave or through a loss of stability leading to complex patterns of propagation.
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Grimshaw, R., E. Pelinovsky, T. Talipova, and O. Kurkina. "Internal solitary waves: propagation, deformation and disintegration." Nonlinear Processes in Geophysics 17, no. 6 (November 17, 2010): 633–49. http://dx.doi.org/10.5194/npg-17-633-2010.
Abstract:
Abstract. In coastal seas and straits, the interaction of barotropic tidal currents with the continental shelf, seamounts or sills is often observed to generate large-amplitude, horizontally propagating internal solitary waves. Typically these waves occur in regions of variable bottom topography, with the consequence that they are often modeled by nonlinear evolution equations of the Korteweg-de Vries type with variable coefficients. We shall review how these models are used to describe the propagation, deformation and disintegration of internal solitary waves as they propagate over the continental shelf and slope.
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Ghahraman, Arash, and Gyula Bene. "Bifurcation Analysis and Propagation Conditions of Free-Surface Waves in Incompressible Viscous Fluids of Finite Depth." Fluids 8, no. 6 (May 31, 2023): 173. http://dx.doi.org/10.3390/fluids8060173.
Abstract:
Viscous linear surface waves are studied at arbitrary wavelength, layer thickness, viscosity, and surface tension. We find that in shallow enough fluids no surface waves can propagate. This layer thickness is determined for some fluids, water, glycerin, and mercury. Even in any thicker fluid layers, propagation of very short and very long waves is forbidden. When wave propagation is possible, only a single propagating mode exists for a given horizontal wave number. In contrast, there are two types of non-propagating modes. One kind of them exists at all wavelength and material parameters, and there are infinitely many such modes for a given wave number, distinguished by their decay rates. The other kind of non-propagating mode that is less attenuated may appear in zero, one, or two specimens. We notice the presence of two length scales as material parameters, one related to viscosity and the other to surface tension. We consider possible modes for a given material on the parameter plane layer thickness versus wave number and discuss bifurcations among different mode types. Motion of surface particles and time evolution of surface elevation is also studied at various parameters in glycerin, and a great variety of behaviour is found, including counterclockwise surface particle motion and negative group velocity in wave propagation.
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Kostik, R., and N. Shchukina. "Properties of sound wave propagation in the solar faculae." Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 63 (2021): 10–14. http://dx.doi.org/10.17721/btsnua.2021.63.10-14.
Abstract:
The results of observations of the faculae region near the center of the solar disk, which were obtained on the German Vacuum Tower Telescope VTT (Tenerife, Spain) are discussed. It is shown that the contrast (brightness) of the facula increases non-monotonouslywith an increase of the magnetic field strength, and, starting from the strength 140 mTl, it decreases.This is contrary to the currently accepted explanation of the increased brightness of facular regions as a result of the Wilson effect. The facular brightness in the upper chromosphere strongly depends on the propagation direction of sound waves. The regions of the facula, where the upward propagating waves are observed, look brighter than the regions in which the waves propagate in the opposite direction from the photosphere to the chromosphere. Dependence of the facular brightness on the wave propagation direction is caused by the fact that upward sound waves, for some reason, prefer to propagate in those regions of the solar facula where the magnetic field strength is above the average value. On the contrary, downward waves are observed in areas where the magnetic field is below average.
34
Volpert, Vit, and Vl Volpert. "Propagation of frontal polymerization—crystallization waves." European Journal of Applied Mathematics 5, no. 2 (June 1994): 201–15. http://dx.doi.org/10.1017/s0956792500001406.
Abstract:
We consider polymerization–crystallization waves in a cylindrical reactor, in which monomer is converted to polymer in a planar front. The polymer is subsequently crystallized in a wider zone behind the front. Specifically, we study uniformly propagating polymerization–crystallization waves, and determine profiles of temperature, and concentrations of polymer and crystallized polymer, as well as the propagation velocity. A linear stability analysis of the travelling wave solutions indicates the possibility of Hopf bifurcation, which describes the transition to the experimentally observed spinning mode of propagation, in which a hot spot is observed to propagate along a helical path on the surface of the cylinder. Since conditions at the time of conversion determine the nature of the polymer produced, spiral hollows, which trace out a helical path, appear on the surface of the crystallized polymer product.
35
Dormann, Dirk, and Cornelis J. Weijer. "Propagating chemoattractant waves coordinate periodic cell movement inDictyosteliumslugs." Development 128, no. 22 (November 15, 2001): 4535–43. http://dx.doi.org/10.1242/dev.128.22.4535.
Abstract:
Migration and behaviour of Dictyostelium slugs results from coordinated movement of its constituent cells. It has been proposed that cell movement is controlled by propagating waves of cAMP as during aggregation and in the mound. We report the existence of optical density waves in slugs; they are initiated in the tip and propagate backwards. The waves reflect periodic cell movement and are mediated by cAMP, as injection of cAMP or cAMP phosphodiesterase disrupts wave propagation and results in effects on cell movement and, therefore, slug migration. Inhibiting the function of the cAMP receptor cAR1 blocks wave propagation, showing that the signal is mediated by cAR1. Wave initiation is strictly dependent on the tip; in decapitated slugs no new waves are initiated and slug movement stops until a new tip regenerates. Isolated tips continue to migrate while producing waves. We conclude from these observations that the tip acts as a pacemaker for cAMP waves that coordinate cell movement in slugs.Movies available on-line
36
Melito, Lorenzo, Matteo Postacchini, Alex Sheremet, Joseph Calantoni, Gianluca Zitti, Giovanna Darvini, and Maurizio Brocchini. "Wave-Current Interactions and Infragravity Wave Propagation at a Microtidal Inlet." Proceedings 2, no. 11 (August 2, 2018): 628. http://dx.doi.org/10.3390/proceedings2110628.
Abstract:
Recent studies have shown that wave blocking occurs at river mouths with strong currents typically preventing relatively short period sea and swell waves from propagating up the river. However, observations demonstrate that lower frequency waves, so-called infragravity waves, do pass through and propagate up the river, particularly during storm events. We present observations from the Misa River estuary of infragravity wave propagation up the river during storm conditions. A model of the complex nonlinear interactions that drive infragravity waves is presented. The results are discussed in the context of an observed river mouth bar formed in the lower reach of the Misa River.
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Chandran, A., and R. L. Collins. "Stratospheric sudden warming effects on winds and temperature in the middle atmosphere at middle and low latitudes: a study using WACCM." Annales Geophysicae 32, no. 7 (July 28, 2014): 859–74. http://dx.doi.org/10.5194/angeo-32-859-2014.
Abstract:
Abstract. A stratospheric sudden warming (SSW) is a dynamical phenomenon of the wintertime stratosphere caused by the interaction between planetary Rossby waves propagating from the troposphere and the stratospheric zonal-mean flow. While the effects of SSW events are seen predominantly in high latitudes, they can also produce significant changes in middle and low latitude temperature and winds. In this study we quantify the middle and low latitude effects of SSW events on temperature and zonal-mean winds using a composite of SSW events between 1988 and 2010 simulated with the specified dynamics version of the Whole Atmosphere Community Climate Model (WACCM). The temperature and wind responses seen in the tropics also extend into the low latitudes in the other hemisphere. There is variability in observed zonal-mean winds and temperature depending on the observing location within the displaced or split polar vortex and propagation direction of the planetary waves. The propagation of planetary waves show that they originate in mid–high latitudes and propagate upward and equatorward into the mid-latitude middle atmosphere where they produce westward forcing reaching peak values of ~ 60–70 m s−1 day−1. These propagation paths in the lower latitude stratosphere appear to depend on the phase of the quasi-biennial oscillation (QBO). During the easterly phase of the QBO, waves originating at high latitudes propagate across the equator, while in the westerly phase of the QBO, the planetary waves break at ~ 20–25° N and there is no propagation across the equator. The propagation of planetary waves across the equator during the easterly phase of the QBO reduces the tropical upwelling and poleward flow in the upper stratosphere.
38
Jayanti, Nuning, Ashari Wicaksono, and Adi Purwandana. "Characterization of solitary internal waves in the northern Bali waters." BIO Web of Conferences 89 (2024): 01006. http://dx.doi.org/10.1051/bioconf/20248901006.
Abstract:
Internal solitary wave (ISW) is an underwater wave, formed due to the evolution of internal tides. The presence of breaking ISWs in coastal areas can potentially influence coastal ecosystems through cross-shelf exchange mechanisms. The southern waters of the Kangean Island and the eastern waters of the Madura Island, known also as part of the northern Bali waters, have been an active habitat for ISW propagation. This study aims to identify and characterize ISW which potentially breaking onshore the Southern Kangean Waters (SKW) and the Eastern Madura Waters (EMW) using Sentinel 1 SAR (Synthetic Aperture Radar) imagery. ISW characterization was carried out using the Korteweg-de Vries (KdV) model. The ISW amplitudes which propagate to EMW varies from 1 - 28 m with a propagation speed of 1.60 - 1.98 m/s, while the ISW which propagate to the SKW has an amplitude of 1 - 60 m with a propagation speed of 0.83 to 2.17 m/s. The results show that the ISW propagating to the SKW has stronger amplitude, phase velocity, and horizontal-vertical velocities than the ISW propagating to the EMW. The maximum speed of the horizontal current triggered by ISW leading to the EMW is 0.03 - 0.17 m/s and the vertical velocity 0.11 - 4.53 cm/s; the maximum speed of horizontal velocity leading to the SKW is 0.02 - 1.29 m/s and the maximum speed of the vertical velocity 0.04 - 19.03 cm/s.
39
Giongo, Gabriel Augusto, José Valentin Bageston, Cosme Alexandre Oliveira Barros Figueiredo, Cristiano Max Wrasse, Hosik Kam, Yong Ha Kim, and Nelson Jorge Schuch. "Gravity Wave Investigations over Comandante Ferraz Antarctic Station in 2017: General Characteristics, Wind Filtering and Case Study." Atmosphere 11, no. 8 (August 18, 2020): 880. http://dx.doi.org/10.3390/atmos11080880.
Abstract:
This work presents the characteristics of gravity waves observed over Comandante Ferraz Antarctic Station (EACF: 62.1° S, 58.4° W). A total of 122 gravity waves were observed in 34 nights from March to October 2017, and their parameters were obtained by using the Fourier Transform spectral analysis. The majority of the observed waves presented horizontal wavelength ranging from 15 to 35 km, period from 5 to 20 min, and horizontal phase speed from 10 to 70 ± 2 m·s−1. The propagation direction showed an anisotropic condition, with the slower wave propagating mainly to the west, northwest and southeast directions, while the faster waves propagate to the east, southeast and south. Blocking diagrams for the period of April–July showed a good agreement between the wave propagation direction and the blocking positions, which are eastward oriented while the waves propagate mainly westward. A case study to investigate wave sources was conducted for the night of 20–21 July, wherein eight small-scale and one medium-scale gravity waves were identified. Reverse ray tracing model was used to investigate the gravity wave source, and the results showed that six among eight small-scale gravity waves were generated in the mesosphere. On the other hand, only two small-scale waves and the medium-scale gravity wave had likely tropospheric or stratospheric origin, however, they could not be associated with any reliable source.
40
Lammers, Wim J. E. P., Luc Ver Donck, Betty Stephen, Dirk Smets, and Jan A. J. Schuurkes. "Origin and propagation of the slow wave in the canine stomach: the outlines of a gastric conduction system." American Journal of Physiology-Gastrointestinal and Liver Physiology 296, no. 6 (June 2009): G1200—G1210. http://dx.doi.org/10.1152/ajpgi.90581.2008.
Abstract:
Slow waves are known to originate orally in the stomach and to propagate toward the antrum, but the exact location of the pacemaker and the precise pattern of propagation have not yet been studied. Using assemblies of 240 extracellular electrodes, simultaneous recordings of electrical activity were made on the fundus, corpus, and antrum in open abdominal anesthetized dogs. The signals were analyzed off-line, pathways of slow wave propagation were reconstructed, and slow wave velocities and amplitudes were measured. The gastric pacemaker is located in the upper part of the fundus, along the greater curvature. Extracellularly recorded slow waves in the pacemaker area exhibited large amplitudes (1.8 ± 1.0 mV) and rapid velocities (1.5 ± 0.9 cm/s), whereas propagation in the remainder of the fundus and in the corpus was slow (0.5 ± 0.2 cm/s) with low-amplitude waveforms (0.8 ± 0.5 mV). In the antrum, slow wave propagation was fast (1.5 ± 0.6 cm/s) with large amplitude deflections (2.0 ± 1.3 mV). Two areas were identified where slow waves did not propagate, the first in the oral medial fundus and the second distal in the antrum. Finally, recordings from the entire ventral surface revealed the presence of three to five simultaneously propagating slow waves. High resolution mapping of the origin and propagation of the slow wave in the canine stomach revealed areas of high amplitude and rapid velocity, areas with fractionated low amplitude and low velocity, and areas with no propagation; all these components together constitute the elements of a gastric conduction system.
41
Bahari, K., N. S. Petrukhin, and M. S. Ruderman. "Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes." Monthly Notices of the Royal Astronomical Society 496, no. 1 (May 23, 2020): 67–79. http://dx.doi.org/10.1093/mnras/staa1442.
Abstract:
ABSTRACT We study the propagation and stability of kink waves in a twisted magnetic tube with the flow. The flow velocity is assumed to be parallel to the magnetic field, and the magnetic field lines are straight outside the tube. The density is constant inside and outside of the tube, and it monotonically decreases from its value inside the tube to that outside in the transitional or boundary layer. The flow speed and magnetic twist monotonically decrease in the transitional layer from their values inside the tube to zero outside. Using the thin tube and thin boundary layer (TTTB) approximation, we derived the dispersion equation determining the dependence of the wave frequency and decrement/increment on the wavenumber. When the kink wave frequency coincides with the local Alfvén frequency at a resonant surface inside the transitional layer, the kink wave is subjected to either resonant damping or resonant instability. We study the properties of kink waves in a particular unperturbed state where there is no flow and magnetic twist in the transitional layer. It is shown that in a tube with flow, the kink waves can propagate without damping for particular values of the flow speed. Kink waves propagating in the flow direction either damp or propagate without damping. Waves propagating in the opposite direction can either propagate without damping, or damp, or become unstable. The theoretical results are applied to the problem of excitation of kink waves in spicules and filaments in the solar atmosphere.
42
Jaimes, C., and V. Fedun. "Qualitative analysis of wave propagation in a 3-D magnetic flux tube." Proceedings of the International Astronomical Union 3, S247 (September 2007): 355–59. http://dx.doi.org/10.1017/s1743921308015081.
Abstract:
AbstractIn this work wave propagation in a 3-D magnetic flux tube is solved numerically. The aim is to find interaction between kink waves and higher order modes (flute modes).A 60x60x60 cube is set up, containing a vertically oriented uniform magnetic flux tube, to solve numerically. Waves are observed propagating after triggering them with solution to the linearized system.The waves propagate acquiring a distinctive shape (seen in the crosscut of the tube at an arbitrary height showing the radial velocity maps). It is discarded that this is caused by the existence of higher order modes and is found that the radial dependence of the phase speed creates the motion.It was also found that the study of the profile of the radial velocity map of a slice of the system is a very intuitive way of analysing the modes of waves propagating through the flux tube.
43
Zhang, Dongliang, Tong W. Fei, and Yi Luo. "Improving reverse time migration angle gathers by efficient wavefield separation." GEOPHYSICS 83, no. 2 (March 1, 2018): S187—S195. http://dx.doi.org/10.1190/geo2017-0348.1.
Abstract:
Angle-domain common-image gathers (ADCIGs) play an important role for migration quality control and velocity analysis. ADCIGs can be constructed by using optical flow to compute propagation directions of seismic waves, which originate and propagate from source and receiver locations. When upgoing and downgoing waves interfere with each other, the optical flow method can generate incorrect propagation angles and produce problematic ADCIGs. To overcome this problem, separating upgoing and downgoing waves is required. The challenge is that separating the wavefields often requires huge memory to store all the snapshots of the propagating 3D wavefields. We have developed a computationally efficient algorithm to separate the wavefields into upgoing and downgoing waves by storing only one additional snapshot of the wavefields at a single time step. Applying the optical flow method on the separated downgoing wavefield produces improved ADCIGs; the improvements are well-verified by tests on synthetic and field data sets.
44
Dias, Juliana, and Olivier Pauluis. "Convectively Coupled Waves Propagating along an Equatorial ITCZ." Journal of the Atmospheric Sciences 66, no. 8 (August 1, 2009): 2237–55. http://dx.doi.org/10.1175/2009jas3020.1.
Abstract:
Abstract The dynamics of convectively coupled gravity waves traveling over a precipitating region are analyzed in an idealized model for the large-scale atmospheric circulation. The model is composed of a shallow water system coupled to an advection equation for moisture through the convection term, utilizing a quasi-equilibrium relaxation to moisture closure. Here the authors investigate the model in the strict quasi-equilibrium (SQE) of infinitely short relaxation time. This framework is applied to study the behavior of a disturbance propagating along a narrow precipitation band, similar to the intertropical convergence zone (ITCZ). For an ITCZ width on the order of the equatorial Rossby radius, Kelvin waves propagate at the moist gravity wave speed (about 15 m s−1), whereas for a narrow ITCZ, the propagation speed is comparable to the dry gravity wave (about 50 m s−1). It is also shown that a Kelvin wave propagating along a narrow precipitation region exhibits a meridional circulation that modulates the precipitation rate and affects the propagation speed of the wave.
45
Rodin, A. A., N. A. Rodina, A. A. Kurkin, and E. N. Pelinovsky. "The influence of nonlinear interaction on the evolution of waves in a shallow basin." Известия Российской академии наук. Физика атмосферы и океана 55, no. 4 (September 17, 2019): 82–86. http://dx.doi.org/10.31857/s0002-351555482-86.
Abstract:
The influence of counter interaction of nonlinear wave in the shallow water has been studied. It is shown that such an interaction leads to a change in the phase of propagation of the main wave, which is forced to propagate along the flow induced by the counter-propagating wave. Estimates of the height of the non-breaking wave at the moment of interaction are in agreement with theoretical predictions. The phase shift in the interaction of non-breaking waves is small enough, but becomes noticeable in the case of the breaking waves motion.
46
Mabie, Justin, and Terence Bullett. "Multiple Cusp Signatures in Ionograms Associated with Rocket-Induced Infrasonic Waves." Atmosphere 13, no. 6 (June 12, 2022): 958. http://dx.doi.org/10.3390/atmos13060958.
Abstract:
We are interested in understanding how and when infrasonic waves propagate in the thermosphere, specifying the physical properties of those waves, and understanding how they affect radio wave propagation. We use a combination of traditional ionosonde observations and fixed frequency Doppler soundings to make high quality observations of vertically propagating infrasonic waves in the lower thermosphere/bottom side ionosphere. The presented results are the first simultaneous observations of infrasonic wave-induced deformations in ionograms and high-time-resolution observations of corresponding plasma displacements. Deformations in ionospheric echoes, which manifest as additional cusps and range variations, are shown to be caused by infrasonic wave-induced plasma displacements.
47
Haddow, J. B., and L. Jiang. "Finite Amplitude Azimuthal Shear Waves in a Compressible Hyperelastic Solid." Journal of Applied Mechanics 68, no. 2 (June 1, 2000): 145–52. http://dx.doi.org/10.1115/1.1334862.
Abstract:
Lagrangian equations of motion for finite amplitude azimuthal shear wave propagation in a compressible isotropic hyperelastic solid are obtained in conservation form with a source term. A Godunov-type finite difference procedure is used along with these equations to obtain numerical solutions for wave propagation emanating from a cylindrical cavity, of fixed radius, whose surface is subjected to the sudden application of a spatially uniform azimuthal shearing stress. Results are presented for waves propagating radially outwards; however, the numerical procedure can also be used to obtain solutions if waves are reflected radially inwards from a cylindrical outer surface of the medium. A class of strain energy functions is considered, which is a compressible generalization of the Mooney-Rivlin strain energy function, and it is shown that, for this class, an azimuthal shear wave can not propagate without a coupled longitudinal wave. This is in contrast to the problem of finite amplitude plane shear wave propagation with the neo-Hookean generalization, for which a shear wave can propagate without a coupled longitudinal wave. The plane problem is discussed briefly for comparison with the azimuthal problem.
48
Mehta, Dhvanit, Andrew J. Gerrard, Yusuke Ebihara, Allan T. Weatherwax, and Louis J. Lanzerotti. "Short-period mesospheric gravity waves and their sources at the South Pole." Atmospheric Chemistry and Physics 17, no. 2 (January 20, 2017): 911–19. http://dx.doi.org/10.5194/acp-17-911-2017.
Abstract:
Abstract. The sourcing locations and mechanisms for short-period, upward-propagating gravity waves at high polar latitudes remain largely unknown. Using all-sky imager data from the Amundsen–Scott South Pole Station, we determine the spatial and temporal characteristics of 94 observed small-scale waves in 3 austral winter months in 2003 and 2004. These data, together with background atmospheres from synoptic and/or climatological empirical models, are used to model gravity wave propagation from the polar mesosphere to each wave's source using a ray-tracing model. Our results provide a compelling case that a significant proportion of the observed waves are launched in several discrete layers in the tropopause and/or stratosphere. Analyses of synoptic geopotentials and temperatures indicate that wave formation is a result of baroclinic instability processes in the stratosphere and the interaction of planetary waves with the background wind fields in the tropopause. These results are significant for defining the influences of the polar vortex on the production of these small-scale, upward-propagating gravity waves at the highest polar latitudes.
49
Musayev, Janat, and Algazy Zhauyt. "Analysis of Disturbing Influence of Traffic Load on Soil Body." Advances in Materials Science and Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/318289.
Abstract:
Stress waves propagate in soil in case of earthquake and man-made effects (traffic flow, buried explosions, shield-driven pipes and tunnels, etc.). The wave point-sources are those located at the distances equal to more than two waves lengths, which significantly simplifies solving of a problem of these waves’ strength evaluation. Distribution of stress and displacement by the stress waves propagation in elastic medium is a complex pattern. The stress distribution in propagating waves depends on the type and form of source, conditions of the source contact with medium, and properties of mediums in the vicinity of the source. The point-sources and their combinations are selected in such a way to model an influence of machines and processes on soil body in case of shield-driven pipes (tunnels).
50
Sun, L., W. Wan, F. Ding, and T. Mao. "Gravity wave propagation in the realistic atmosphere based on a three-dimensional transfer function model." Annales Geophysicae 25, no. 9 (October 2, 2007): 1979–86. http://dx.doi.org/10.5194/angeo-25-1979-2007.
Abstract:
Abstract. In order to study the filter effect of the background winds on the propagation of gravity waves, a three-dimensional transfer function model is developed on the basis of the complex dispersion relation of internal gravity waves in a stratified dissipative atmosphere with background winds. Our model has successfully represented the main results of the ray tracing method, e.g. the trend of the gravity waves to travel in the anti-windward direction. Furthermore, some interesting characteristics are manifest as follows: (1) The method provides the distribution characteristic of whole wave fields which propagate in the way of the distorted concentric circles at the same altitude under the control of the winds. (2) Through analyzing the frequency and wave number response curve of the transfer function, we find that the gravity waves in a wave band of about 15–30 min periods and of about 200–400 km horizontal wave lengths are most likely to propagate to the 300-km ionospheric height. Furthermore, there is an obvious frequency deviation for gravity waves propagating with winds in the frequency domain. The maximum power of the transfer function with background winds is smaller than that without background winds. (3) The atmospheric winds may act as a directional filter that will permit gravity wave packets propagating against the winds to reach the ionospheric height with minimum energy loss.