Propagation Of Surface Waves Research Articles

Surface Wave Developments under Tropical Cyclone Goni (2020): Multi-Satellite Observations and Parametric Model Comparisons

Over the Philippine Sea, the tropical cyclone (TC) Goni reaches category 5 on 29–31 October 2020. Multi-satellite observations, including CFOSAT SWIM/SCAT and Sentinel-1 SAR data, are jointly analyzed to assess the performances of a parametric model. Recently developed to provide a fast estimation of surface wave developments under rapidly evolving TCs, this full 2D parametric model (KYCM) and its simplified self-similar solutions (TC-wave geophysical model function (TCW GMF)) are thoroughly compared with satellite observations. TCW GMF provides immediate first-guess estimates, at any location in space and time, for the significant wave height, wavelength, and wave direction parameters. Moving cyclones trigger strong asymmetrical wave fields, associated to a resonance between wave group velocity and TC heading velocity. For TC Goni, this effect is well evidenced and captured, leading to extreme waves reaching up to 8 m, further outrunning as swell systems with wavelengths about 200–250 m in the TC heading direction, slightly shifted leftwards. Considering wind field constrained with very highly resolved Sentinel-1 SAR measurements and medium resolution CFOSAT SCAT data, quantitative agreements between satellite measurements and KYCM/TCW GMF results are obtained. Far from the TC inner core (∼10 radii of maximum wind speed), the superposition of outrunning swell systems and local wind waves estimates leads to Hs values very close to altimeter measurements. This case study demonstrates the promising capabilities to combine multi-satellite observations, with analytical self-similar solutions to advance improved understandings of surface wave generation under extreme wind conditions.

Scale effects on the torsional surface waves propagation in an initially stressed dissipative nanoplate

The effects of small length scale on the torsional surface waves propagating in a pre-stressed dissipative nanoplate were examined in this paper. Biot’s incremental deformation principle as well as nonlocal elasticity theory were implemented to form the governing and frequency equations of torsional surface waves in nanoplate under considered conditions. In this work, we proposed a new approach to determine the phase velocity of torsional disturbances. Different categories are used to investigate the dispersion relations such as: wave number, scale coefficient, initial stress parameter, and dissipation coefficient. The results show that small length scale influences causes torsional dispersion of the wave propagation, which disappear in local elasticity theory. In addition, it is recognized that the torsional surface waves propagating in the pre-stressed dissipative nanoplates can be differentiated in a clear manner from those propagated in the absence of small length scale effects. The initial stress parameter can also be utilized to change the characteristics of the torsional surface wave's phase velocity in nanoplates. It is also observed that, the dissipation has a great effect on the phase velocity of torsional surface waves in propagating in the nanoplate. Therefore, this research is theoretically useful to convey information on nonlocal and dissipation properties of the nanomaterials: for example, through a precise measurement of the phase velocity of torsional surface wave propagates in a nanocomposite material by presence of the medium’s dissipation. This work could be useful in understanding the way of designing the Nano devices and Nano resonators.

New abundant solitary wave structures for a variety of some nonlinear models of surface wave propagation with their geometric interpretations

The propagation of waves of water on the surface is characterized by various mathematical models. In this work, we adopt the simplest equation method as well as the Kudryashov's new function method, to a variety of some nonlinear models of surface wave propagation to extract their abundant solitary wave structures. These nonlinear models include the Benjamin‐Bona‐Mahony (BBM) equation, the Ostrovsky (OS) equation, the Ostrovsky‐Benjamin‐Bona‐Mahony (OS‐BBM) equation, and the Boussinesq system of equations. Based on the solutions of two distinct auxiliary equations, various wave solutions are successfully obtained. In addition, the geometric interpretations of the obtained solutions are analyzed. To illuminate the physical nature of the obtained solutions of this paper, some graphical representations (numerical simulations) of the acquired solutions have been depicted in two‐dimensional density, two‐ and three‐dimensional graphs. Furthermore, a comparison between the obtained results of this paper and the solutions for the considered models obtained in the literature is also provided. It is shown that the used approaches are very effective and powerful strategies for a wider class of nonlinear partial differential equations in physical problems.

Centimeter‐Scale Propagation of Optical Surface Waves at Visible Wavelengths

AbstractGuiding and confining light at interfaces is crucial for applications involving light–matter interactions, such as surface spectroscopy, nonlinear optics, and quantum information technology. While dielectric surface waves offer promising perspectives for strong light confinement at non‐absorbing interfaces, their capacity has not yet been widely explored. This article focuses on the propagation properties of optical modes supported at the free surface of a 1D photonic crystal. The contributions of intrinsic and extrinsic loss mechanisms are investigated. Structures optimized to support long propagating optical surface waves are designed and fabricated. This work experimentally demonstrates, for the first time, the existence of optical surface waves capable of propagating over centimeter‐scale distances in the visible spectral range. The results open new perspectives for the use of optical surface waves in integrated optics and enhanced light–matter interactions.

Design of a finline antenna for current drive in TST-2

A novel “finline” antenna was designed to excite lower-hybrid waves (LHWs) for plasma current drive at 2.45 GHz in the TST-2 spherical tokamak. A periodic fin array acts as a transmission line for electromagnetic surface waves. Cold tests confirmed propagation of the electromagnetic surface wave on the fin array which was dominantly Transverse Magnetic (TM). Unlike the conventional waveguide array “grill” antenna, the finline antenna requires only two ports to feed all the elements, and calculations show that there is little reflection regardless of the plasma conditions in front of the antenna. Characteristics of the microwave transmission on the fin array were investigated using a three-dimensional full-wave simulation and the fin geometry was tuned to achieve the desired refractive index. Coupling to LHWs under typical TST-2 scrape-off layer conditions was confirmed by the simulation. To demonstrate LHW excitation, the finline antenna was energized in the presence of a plasma generated by another 200 MHz LH antenna. The x-ray radiation showed strong enhancement during the finline antenna pulse which indicated successful generation of fast electrons by LHWs.

Lie Symmetries, Closed-Form Solutions, and Various Dynamical Profiles of Solitons for the Variable Coefficient (2+1)-Dimensional KP Equations

This investigation focuses on two novel Kadomtsev–Petviashvili (KP) equations with time-dependent variable coefficients that describe the nonlinear wave propagation of small-amplitude surface waves in narrow channels or large straits with slowly varying width and depth and non-vanishing vorticity. These two variable coefficients, Kadomtsev–Petviashvili (VCKP) equations in (2+1)-dimensions, are the main extensions of the KP equation. Applying the Lie symmetry technique, we carry out infinitesimal generators, potential vector fields, and various similarity reductions of the considered VCKP equations. These VCKP equations are converted into nonlinear ODEs via two similarity reductions. The closed-form analytic solutions are achieved, including in the shape of distinct complex wave structures of solitons, dark and bright soliton shapes, double W-shaped soliton shapes, multi-peakon shapes, curved-shaped multi-wave solitons, and novel solitary wave solitons. All the obtained solutions are verified and validated by using back substitution to the original equation through Wolfram Mathematica. We analyze the dynamical behaviors of these obtained solutions with some three-dimensional graphics via numerical simulation. The obtained variable coefficient solutions are more relevant and useful for understanding the dynamical structures of nonlinear KP equations and shallow water wave models.

Generation of quasi-cylindrical waves during inhomogeneous heating of a metal by a focused laser pulse

The generation of low-frequency quasi-cylindrical and surface waves generated by a long pulse of laser radiation focused into a narrow strip on the metal surface is studied. Waves are generated by non-linear currents arising from inhomogeneous heating of electrons. It is shown that the total low-frequency field is mainly determined by the quasi-cylindrical wave field. The angular and frequency distributions of the generated radiation energy have been studied. The range of angles in which it is necessary to take into account the near-surface structure of quasi-cylindrical waves is established.

Nonlinear piezoelectric surface acoustic waves.

The theory for nonlinear surface acoustic waves in crystals developed using Hamiltonian mechanics [Hamilton, Il'inskii, and Zabolotskaya, J. Acoust. Soc. Am. 105, 639 (1999)] is modified to account for piezoelectric material properties. The derived spectral evolution equations permit analysis of nonlinear surface wave propagation along a cut surface of any orientation with respect to the crystallographic axes and for piezoelectric crystals with any symmetry. Numerical simulations of waveform distortion in the particle velocity and electric field components are presented for surface wave propagation in Y-cut lithium niobate along the X- and Z-crystallographic axes. The influence of piezoelectricity is illustrated by comparing the nonlinear evolution of waveforms along a surface bounded by a vacuum (free space) and an ideal conductor (short circuit). Contributions to the nonlinearity from elasticity, piezoelectricity, electrostriction, and dielectricity are quantified separately for the two boundary conditions.

Propagation of Rayleigh-type surface waves in a layered piezoelectric nanostructure with surface effects

Propagation of Rayleigh-type surface waves in a layered piezoelectric nanostructure with surface effects

Low-Profile Substrate Integrated Choke Rings for GNSS Multipath Mitigation

In this article, a novel technique for the miniaturization of corrugated structures is presented, and multifolded corrugations (MFCs) are introduced. The miniaturization is achieved by implementing multiple folds or slits inside corrugations. The proposed miniaturization technique is modeled using the modal expansion method. An equivalent circuit is extracted, which precisely models the surface impedance of the proposed MFCs. A time-efficient design procedure is presented based on the equivalent circuit model, and a dual-band double-folded substrate integrated choke ring (DFSICR) structure is designed to suppress the propagation of surface waves over the main global navigation satellite system (GNSS) frequency bands: L1 (1573–1587 MHz) and L2 (1215–1240 MHz). The DFSICR demonstrates significant multipath mitigation capabilities, close to that of a classic choke ring, while it eliminates the drawbacks of a conventional choke ring, such as large size, heaviness, costly fabrication, and inability to integrate with printed circuit board (PCB) structures. An example design shows miniaturization of 85% in height and 38% in diameter compared to the conventional choke ring. A prototype is fabricated using FR4 laminates, which demonstrates a weight reduction of more than 90% compared to the classic choke ring. The measurement results confirm the validity of the proposed technique.

Analysis of thermal effect on propagation of Rayleigh surface waves in a composite structure

Analysis of thermal effect on propagation of Rayleigh surface waves in a composite structure

Plasma-thermal-elastic waves of semiconductor induced by laser pulses with hydrostatic initial stress and the hyperbolic two-temperature theory

The hyperbolic two-temperature theory under the effect of initial stress is used to investigate the surface wave propagations on a semiconductor medium. The governing equations are taken under the impact of the photo-thermal theory during the photo-excitation transport processes under the initial stress. The semiconductor medium is affected on the outer surface by a pulsed laser. The main equations are studied when they are coupled between the photo-thermal theory and thermoelasticity theory in two-dimensional (2D) deformation. Some thermoelasticity models (Lord–Shulman (LS), Green–Lindsay (GL) and the classical dynamical coupled theory (CD)) with the effect of relaxation time are used. The analytical solutions are obtained when the combination processes between the hyperbolic two-temperature theory and photo-thermoelasticity theory under the impact of initial stress and pulsed laser are considered. The harmonic wave is used to attain exact expressions on the main physical fields under photo-excitation processes. The mechanical, thermal and recombination plasma loads are applied at the medium-free surface to get the complete solutions of the basic studied physical fields. Some comparisons are made between the three thermoelasticity models under the electrical impact of thermoelectric coupling parameter, and there are shown graphically and discussed.

Spectral gaps for the linear water‐wave problem in a channel with thin structures

AbstractWe consider the linear water‐wave problem in a periodic channel , which consists of infinitely many identical containers and connecting thin structures. The connecting canals are assumed to be of constant, positive length, but their depth is proportional to a small parameter h. Motivated by applications to surface wave propagation phenomena, we study the band‐gap structure of the essential spectrum in the linear water‐wave system, which forms a spectral problem where the spectral parameter appears in the Steklov boundary condition posed on the free water surface. We show that for small h there exists a large number of spectral gaps and also find asymptotic formulas for the position of the gaps as : the endpoints are determined within corrections of order . The width of the first spectral band is shown to be .

Guided acoustic waves at periodically structured edges: Linear modes and nonlinear generation of Lamb and surface waves

Acoustic waves are investigated which are guided at the edge (apex line) of a wedge-shaped elastic body or at the edge of an elastic plate. The edges contain a periodic sequence of modifications, consisting either of indentations or inclusions with a different elastic material which gives rise to high acoustic mismatch. Dispersion relations are computed with the help of the finite element method. They exhibit zero-group velocity points on the dispersion branches of edge-localized acoustic modes. These special points also occur at Bloch-Floquet wavenumbers away from the Brillouin zone boundary. Deep indentations lead to flat branches corresponding to largely non-interacting, Einstein-oscillator like vibrations of the tongues between the grooves of the periodic structure. Due to the nonlinearity of the elastic media, quantified by their third-order elastic constants, an acoustic mode localized at a periodically modified edge generates a second harmonic which partly consists of surface and plate modes propagating into the elastic medium in the direction vertical to the edge. This acoustic radiation at the second-harmonic frequency is investigated for an elastic plate and a truncated sharp-angle wedge with periodic inclusions at their edges. Unlike nonlinear bulk wave generation by surface acoustic waves in an interdigital structure, surface and plate mode radiation by edge-localized modes can be visualized directly in laser-ultrasound experiments.

Anisotropic impedance surfaces activated by incident waveform

Abstract Anisotropic impedance surfaces have been used to control surface wave propagation, which has benefited applications across a variety of fields including radio-frequency (RF) and optical devices, sensing, electromagnetic compatibility, wireless power transfer, and communications. However, the responses of these surfaces are fixed once they are fabricated. Although tunable impedance surfaces have been introduced by utilizing power-dependent nonlinear components, such a tuning mechanism is generally limited to specific applications. Here we propose an additional mechanism to achieve tunable anisotropic impedance surfaces by embedding transient circuits that are controllable via the type of incident waveform. By switching between the open and short states of the circuits, it is possible to separately control the unit-cell impedances in two orthogonal directions, thereby changing from an isotropic impedance surface to an anisotropic impedance surface. Our simulation results show that a short pulse strongly propagates for both x and y directions at 3 GHz. However, when the waveform changes to a continuous wave, the transmittance for x direction is reduced to 26%, although still the transmittance for y direction achieves 77%. Therefore, the proposed metasurfaces are capable of guiding a surface wave in a specific direction based on the incident waveform even with the same power level and at the same frequency. Our study paves new avenues regarding the use of surface wave control in applications ranging from wireless communications to sensing and cloaking devices.

Existence and uniqueness of Rayleigh waves in isotropic elastic Cosserat materials and algorithmic aspects

We discuss the propagation of surface waves in an isotropic half space modelled with the linear Cosserat theory of isotropic elastic materials. To this aim we use a method based on the algebraic analysis of the surface impedance matrix and on the algebraic Riccati equation, and which is independent of the common Stroh formalism. Due to this method, a new algorithm which determines the amplitudes and the wave speed in the theory of isotropic elastic Cosserat materials is described. Moreover, this method allows us to prove the existence and uniqueness of a subsonic solution of the secular equation, a problem which remains unsolved in almost all generalized linear theories of elastic materials. Since the results are suitable to be used for numerical implementations, we propose two numerical algorithms which are viable for any elastic material. Explicit numerical calculations are made for aluminium-epoxy in the context of the Cosserat model. Since the novel form of the secular equation for isotropic elastic material has not been explicitly derived elsewhere, we establish it in this paper, too.

Резонаторная ячейка с открытым входом на основе диэлектрической пластины на металлической подложке

Possibility of converting the energy of an incident electromagnetic wave to the energy of a surface wave in a dielectric plate on a metal substrate has been confirmed through numerical simulation. To transfer energy between waves of different structures, a diffraction grating placed on the surface of the plate is used. Energy is retained in the plate through the formation of a surface wave resonator by introducing aflush metal walls along the plate’s ends. Thus, the resonant cell with open entrance has been suggested – the energy enters the cell through the whole lit surface of the plate. It is assumed that the dielectric has small losses, and the diffraction grating on its surface consists of the identical bars, which are made of the same dielectric and have small cross section. The resonance in the form of sharp increase of the standing wave amplitude inside the plate, compared to the incident wave amplitude, and correspondingly increase of the incident wave’s energy absorption by the plate takes place at some grating periods. The external manifestation of resonance is a decrease of specular scattering from the plate: the observed decrease of plate’s RCS in the ray reflection direction was from several times to more than three orders of magnitude under different conditions. Stability of numerical solution of the problem of diffraction on the suggested cell follows from the observed smooth variation of the condition number in the vicinity of even the deepest plate’s resonant RCS reduction. Efficiency of surface wave generation by diffraction gratings of different types or by arranging other periodical inhomogeneities on the surface or within the volume of dielectric can be compared according to the depth of resonance.

Dispersion characteristics of surface plasmon polaritons in a graphene–plasma–graphene waveguide structure

Theoretical investigations are carried out to study surface wave propagation for a graphene parallel-plate waveguide structure filled with isotropic plasma. The extended wave propagation theory is used. The Kobo formula is used to determine graphene conductivity. Maxwell’s equations (differential form) are used to solve the analytical problem. It is concluded that surface wave propagation can be tuned and controlled by tuning the plasma parameters (plasma frequency and collisional frequency) as well as chemical potential and relaxation time of graphene. Furthermore, the effect of plasma frequency and collisional frequency on the wave attenuation is discussed, and the effect of graphene’s chemical potential, plasma frequency, and collisional frequency on propagation length are also analyzed. The normalized field distribution of plasma medium is also studied. These results may lead to potential applications in optical sensing, communication, and plasma-based optical integrated devices in the gigahertz frequency regime.

Effects of bottom permeability on wave generation by a moving oscillatory disturbance in magneto-hydrodynamics

Generation of magneto-hydrodynamic surface wave by a moving oscillatory disturbance in a finite depth ocean bounded below by a horizontal porous bottom is presented. The governing initial-boundary value problem is solved using Laplace-Fourier transform and an integral form of the surface elevation is obtained. The asymptotic solutions for the free surface elevation are obtained using stationary phase method. The results show that both the steady-state and transient components exist where the latter decays asymptotically and steady-state is reached. It is seen that the bottom permeability has a significant impact on surface elevation. The dispersion relation is also taken into account and the phase and group velocities for deep water and shallow water are analyzed for different values of the parameters in number of figures. The results for limiting case in which the current speed and the porosity vanishes are compared with the calculations investigated earlier.

Radiation of a charged particle bunch moving along a deeply corrugated structure with a relatively small period

We investigate electromagnetic radiation from a bunch moving along a corrugated conductive planar structure. The radiation is analyzed at wavelengths which are much greater than the period of the corrugation. In this case, the theoretical solution can be obtained by the use of equivalent boundary conditions (EBC). Here, we consider the case of deep corrugation, i.e. we assume that the depth of the structure is of the same order as an inverse wavenumber. Using the EBC method we obtain the general solution of the problem and investigate it asymptotically. It is shown that the bunch generates surface waves propagating in the plane of the structure, whereas volume radiation is absent at the frequencies under consideration. The surface radiation is analyzed in detail. In particular, it is demonstrated that, under certain conditions, the properties of the surface waves can be used for the determination of the bunch size. In addition, we consider the energy losses of the bunch. Typical dependences of the energy losses on the corrugation parameters are obtained and analyzed.