Characteristics Of Surface Waves Research Articles

Analysis of different wave characteristics in a fiber-reinforced thermo-piezoelectric rotating medium influenced by gravity

Fiber-reinforced polymer composites possess a lightweight nature, corrosion resistance, high strength, and specific stiffness. As a result, they play a crucial role in the construction and rehabilitation of structures, providing reinforcement with their versatile and beneficial properties. Owing to this, proposed mathematical model is intended to give a detailed analysis of the characteristics of surface waves in a homogeneous, transversely isotropic fiber-reinforced thermo-piezoelectric (FRTPC) composite half-space rotating with uniform angular frequency including Coriolis and centrifugal forces. Recently proposed Moore–Gibson–Thompson thermoelasticity theory with two-temperature is employed to describe the mathematical framework. The free surface is considered to be stress free, electrically shorted/charge free, and thermally insulated/isothermal. The FRTPC structure is analytically modeled by the Strength of Materials technique with the Rule of Mixtures approach. Normal mode technique is used to derive the expression for mechanical stresses, electrical displacement, and temperature gradient. Depending upon four different boundary conditions, corresponding secular equations are derived for the considered half-space. The influence of rotation, gravity, fiber volume fraction, and two-temperature on different wave characteristics (phase velocity, attenuation coefficient, specific loss, and frequency shift) is demonstrated graphically considering PZT-5H epoxy material. Numerical simulation indicates that wave propagates at a finite speed in the FRTPC medium in the case of MGT thermoelastic theory, rather than the infinite speed in the classical thermoelasticity model. The present mathematical study may find its application in designing of gyroscopes, rotation sensors, temperature sensors, and other pyro/piezoelectric surface acoustic wave devices.

Spatial Evolution Characteristics of Plasmapause Surface Wave During a Geomagnetic Storm on 16 July 2017

AbstractBoundary dynamics are crucial for the transport of energy, mass, and momentum in geospace. The recently discovered plasmapause surface wave (PSW) plays a key role in the inner magnetosphere dynamics. However, a comprehensive investigation of spatial variations of the PSW remains absent. In this study, we elucidate the spatial characteristics of a PSW through observations from multiple spacecrafts in the magnetosphere. Following the initiation of the PSW, quasi‐periodic injections of energetic ions, rather than electrons, are suggested to serve as energy source of the PSW. Based on the distinct wave and particle signatures, we categorize the PSW into four regions: seed region, growth region, stabilization region and decay region, spanning from nightside to afternoon plasmapause. These findings advance our understanding of universal boundary dynamics and contribute to a deeper comprehension of the pivotal roles of surface waves in the energy couplings within the magnetosphere‐plasmasphere‐ionosphere system.

Low-order modelling of three-dimensional surface waves in liquid film flow on a rotating disk

Using low-dimensional numerical simulations, we investigate the characteristics of complex and three-dimensional surface waves in a liquid film flowing over a rotating disk, focusing on large flow rates from a nozzle. Existing integral boundary layer (IBL) models, which are based on spatially averaged variables along the direction normal to the disk surface, have primarily focused on the formation of axisymmetric waves under relatively small flow rates. In this study, an extended IBL model that accounts for both laminar and turbulent regimes is developed by considering the non-uniformity of the local flow rate in the spreading film flow and incorporating closure models dependent on the local Reynolds number. Our numerical results successfully capture the generation of concentric waves by an impinging circular liquid jet and their transition into three-dimensional solitary waves. These findings are in good agreement with visualization images and time-series data of free-surface fluctuations from a displacement sensor. The backscattering of small-scale three-dimensional turbulence into large-scale horizontal turbulence inside the film plays a critical role in determining the transition of wave modes and the nonlinear dynamics of the waves in the turbulent regime. Furthermore, the behaviour of three-dimensional waves in the downstream region, including frequent wave coalescence in the transition region and the breakup of small-scale solitons, is distinct from that of gravity-driven falling film flows. The amplitude of the three-dimensional waves is inversely related to the generalized Reynolds number defined for rotating films.

Temperature-Dependent Electromagnetic Surface Wave Supported by Graphene-Loaded Indium Antimonide Planar Structure

In this study, the propagation characteristics of EM surface waves supported by the graphene-coated indium antimonide (InSb) planar waveguide have been investigated theoretically and numerically. The modeling of graphene has been performed by use of Kubo formalism whereas the relative permittivity of indium antimonide has been calculated using Drude’s model. The results for transverse electric (TE) and transverse magnetic (TM) polarized surface waves have been computed analytically and numerically. The major challenge is to model the atomically thick graphene sheet over the InSb grounded slab. To get the temperature-dependent characteristic equation for the electromagnetic surface waves, the surface current boundary conditions’ approach has been employed. The numerical results have been computed for both the TE and TM polarization states and reported that the TE does not support the propagation of surface waves. The dispersion relation, effective mode index, phase speed, propagation length, and field profile have been computed in Mathematica under TM polarization. The graphene and indium antimonide have been found active for low and high Terahertz regions, respectively. As temperature increases, the plasma frequency of the InSb increases due to this reason with the increase of temperature and the resonance frequency, leading to a shift in the dispersion curve. Moreover, with the increase of temperature, the effective wave number of transverse magnetic polarized surface waves also increases. Resultantly, the confinement of such surface waves supported by graphene-loaded InSb increases. It is shown that with the variation of temperature of indium antimonide, the surface waves propagating across the interface can be tuned in the Terahertz region and can be exploited for thermo-optical sensing, near-field communications waveguides, and graphene-based temperature sensor designing.

Complex dispersion analysis of true and pseudo surface waves propagating in two-dimensional viscoelastic seismic metamaterials

In this paper, the wave characteristics of true surface waves (TSWs) and pseudo surface waves (PSWs) in two-dimensional (2D) seismic metamaterials are explored. The 2D seismic metamaterial is formed by placing periodic concrete pillars on the surface of the soil substrate. The complex dispersion curves of the seismic metamaterial are numerically calculated by the ω–kapproach. The Kelvin–Voigt model is adopted to describe the material viscoelasticity. The results show that not only the TSW modes but also the PSW modes should be taken into account to evaluate the mitigation capacity of the seismic metamaterials. Due to the introduction of material viscoelasticity, the TSWs and PSWs convert from the propagative mode to the evanescent mode. When the PSW modes propagate along the substrate surface, their energy gradually leaks into the bulk of the substrate, leading to their transmission coefficient smaller than that of the TSW modes. Compared to the concrete pillars on the substrate surface, the viscoelasticity of the soil substrate plays a more important role in surface wave reduction. Moreover, the wave propagating length in the seismic metamaterials can be predicted by using complex dispersion relations.

Comprehensive index condition assessment of structural concrete based on surface wave techniques

To reliably assess the condition of concrete structures, a surface wave-based comprehensive index has been developed. Considering various factors (e.g., aggregate types) influencing the surface wave-based characteristics, a relative index for concrete condition assessment has presented. To address the conflicts between individual indexes, the weight for each index is determined in accordance with its credibility. The effectiveness of the proposed methodology is verified by using test results from six concrete beams with different void volume ratios. Hereby three characteristics of surface waves (i.e., P- and R-wave velocities, and attenuation coefficient) are used to diagnose the concrete beams. It is found that the comprehensive index has the advantage in handling abnormal measurements of the individual indexes by reducing their weights to lower their influence on the final diagnosis. Comparison of the diagnoses based on the comprehensive index and individual indexes reveals that the comprehensive index performs much better than any other individual index. It matches greatly with the compressive strength of the concrete beams obtained from the destructive test. In conclusion, the proposed methodology presents a single comprehensive diagnostic feature with improved reliability on the fitness of the concrete structures for decision-makers.

Thermally tunable electromagnetic surface waves supported by graphene loaded indium antimonide (InSb) interface

The thermal agitation plays a vital role in tunability of optoelectronic, structural and chemical characteristics of the temperature sensitive materials. Graphene enables the THz optics, due to its unprecedent controlling characteristics over the traditional materials. The influence of temperature on the monolayer graphene is very negligible due to its low free charge carrier density, to enhance the thermal sensitivity of graphene, the graphene loaded temperature sensitive material interface has been proposed. A theoretical analysis has been carried out on temperature dependent propagation characteristics of electromagnetic surface waves supported by the graphene loaded semi-infinite indium antimonide (InSb). The InSb has been taken as temperature sensitive material. The Drude model has been used for the modeling of InSb in the THz region while the modeling of the graphene has been done by random phase approximation-based Kubo’s formulism. To realize the graphene loaded indium antimonide interface, the impedance boundary conditions (IBCs) have been employed. The numerical analysis has been conducted to analyze the influence of temperature on the characteristics of electromagnetic surface waves i.e., dispersion curve, effective mode index (Neff), penetration depth (δ), propagation length (Lp), phase speed (Vp) and field profile, propagating along the graphene loaded InSb. In all the numerical results, the temperature variation has been considered from 200 to 350 K. It has been concluded that the graphene–InSb interface provides more temperature assisted tunability to the interfacial surface modes, commonly known as surface waves, as compared to monolayer graphene. Further, the graphene parameters can play a vital role in the dynamical tuning of electromagnetic surface waves in THz to IR frequency range. The numerically computed results have potential applications in designing of thermo-optical waveguides, temperature assisted communication devices, thermo-optical sensors and near field thermal imaging platforms.

Surface wave and splashing of liquid film by oblique water jet impinging on a vertical plate

Liquid film cooling by jet impingement, known as a common thermal protection technique, is extensively applied in liquid rocket engines. The present work investigates the impact of a water jet onto a vertical plate by high-speed visualization system and laser particle analyzer, with a focus on the characteristics of surface waves and droplets splashing during the formation of liquid film. Depending on whether the jet is broken before impact, two regimes are identified, i.e., droplet or continuous jet impingement regime. The frequency and velocity of the surface wave and the splashing rate are jointly affected by the jet angle and the impingement distance. The splashing is mainly caused by the capillary breakup of the crown film that forms at the edge of the surface wave, and most of the splashing droplets are generated from the top of the crown film. The larger the jet angle, the smaller the wave frequency and velocity, but the higher the splashing rate. A large impingement distance causes a small wave frequency and velocity due to the shift of the impingement regime, further resulting in different tendencies in the splashing rate. A parameter expression for the size distributions of splashing droplets is established by the fitting result of the log-normal distribution and the Rosin-Rammler (R-R) distribution, where the parameters are associated with the jet Weber number.

Dispersion Properties of Surface Waves Decaying in Red-Shifted and Blue-Shifted Gaps in Photonic Hypercrystals

The dispersion characteristics of surface waves for transverse electric and magnetic polarization modes of photonic hypercrystals (PHC) are theoretically explored. PHC are composed of a dielectric and hyperbolic metamaterial (HMM) with thin layers of both metal and dielectric surface waves that decay inside red-shifted gaps have a negative group velocity, whereas surface waves that decay inside traditional blue-shifted gaps have more typical characteristics. Curve plotting is used to elucidate on how these surface waves depend on several other structural properties such as filling factor, widths of HMM and dielectric, frequency range and angle of incidence etc.

Scattering enhancement of partially buried sphere at the water-sand interfaces due to reflected subsonic Rayleigh waves

In view of the development needs of maritime security, the detecting of buried targets over long distances at low frequencies needs to be solved urgently. Through well designed experiments at low frequency (ka = 5–10), this paper presents a study on the scattering echoes from polymethylmethacrylate (PMMA) spheres in partially buried cases (50%, 75% and 100% buried), and the propagation characteristics of subsonic Rayleigh surface waves on the surface of PMMA spheres at the water-sand interface can be clearly observed. It is shown that the fine sand medium with larger impedance brings about smaller circumferential phase and group velocities of subsonic Rayleigh waves on the surface of the PMMA sphere; the resonance peak caused by subsonic Rayleigh waves is shifted toward the low frequency with the deepening of the burial depth, and the offset can be predicted by the circumferential phase velocity of the subsonic Rayleigh wave in different media and burial depth of PMMA sphere, and the experimental and finite element simulation results validate the shift of the Rayleigh resonance peak. The research results of this paper can provide certain reference value for the detection of low frequency buried targets.

Guiding acoustic waves via a gradient index meta-layer

In this work, we propose an efficient approach for controlling acoustic waves through guided mode conversion within a single meta-layer comprised of gradient index metamaterials. By harnessing the subwavelength localization characteristics of acoustic surface waves, the meta-layer can be properly shaped to accommodate arbitrary and prospective trajectories, thus enabling flexible guidance and routing of acoustic waves. Utilizing such a mode conversion mechanism, the acoustic directional transmitter and beam splitter have been devised and numerically demonstrated based on Archimedean spiral structures. These acoustic devices can exhibit a broadband response, achieving transmission efficiency exceeding 80% over a specific bandwidth that can be controlled by the geometry design. The proposed gradient index meta-layer may open new possibilities for acoustic wave manipulation, enabling some promising applications in noise control, information transmission, and energy harvesting.

Experimental investigation on interfacial defect detection for SCCS with conventional and novel contact NDT techniques

In order to ensure the mechanical performance and structural safety of steel–concrete composite structures (SCCS), advanced nondestructive testing (NDT) technique for bonding status at steel–concrete interfaces needs to be developed. In this study, the feasibility of multichannel analysis of surface waves (MASW)-based interfacial debonding detection is validated using the contact sensors array. Herein, the multichannel sensor arrays are composed of piezoceramic lead zirconate titanate patches and high-frequency acceleration meters, respectively. For comparison, the impact-response (IR) method and impact-transmission (IT) method are performed utilizing a force hammer and high-frequency acceleration meters, and corresponding damage imaging algorithms are developed. The applicability of ultrasonic computed tomography (CT) scanning test, scanning impact echo (IE) method, ultrasonic tomography (UT) technique on interfacial debonding detection is further discussed in depth. Research findings indicate that the developed contact MASW measurement can fully capture the variation of dispersion characteristics of surface waves induced by debonding defects in SCCS. The developed IR and IT methods are suitable for detecting interfacial debondings in different dimensions. Besides, the damage nephogram resolution of IR is higher than that of the IT method. In addition, the practicability of traditional ultrasonic CT scanning tests, scanning IE method, and UT techniques using commercial equipment is investigated. Experimental observations show that classical NDT testing techniques are incapable of effectively identifying the existence of interfacial damage and are unsuitable for NDT tests on SCCS. The research findings in this study clearly exhibit the precision and limitation of various contact NDT techniques and lay a solid foundation for interfacial debonding detection in practical SCCS.

Statistical characteristics of sea surface waves derived from buoy measurements in the eastern Guangdong offshore water

The wave characteristics of the eastern Guangdong offshore water were quantified based on 1-year wave observations at a water depth of 60 m. This study statistically analyzed the observed wave characteristics and quantified the variations of the wave parameters and spectrum due to Super Typhoon Mangkhut. Results showed that the dominant and strong wave directions in the northeastern South China Sea were north-eastern and eastern, respectively. The average significant wave height was in the range of 0.7–2.4 m. During Super Typhoon Mangkhut, the maximum wave height and period were 11.3 m and 10–12 s, respectively, and peak spectral density mainly varied between 0.06 and 0.1 Hz. Results of this study can provide a basis for offshore engineering design and are of great significance for marine forecasting and disaster prevention and reduction.

Laser ultrasonic inspection for mechanical properties of materials at high temperature

The measurement of mechanical properties of high-temperature resistant materials at high temperatures is particularly critical, and laser ultrasonic non-destructive testing technology is a prospective approach for measuring mechanical properties in high-temperature environments. Laser ultrasonic propagation models are constructed by finite element analysis, which reveals the effects of different excitation mechanisms on acoustic velocity measurements. It is found that the shear wave in the main propagation direction is hardly detected, and the distinction between shear waves and surface waves in the time domain signal is difficult. Based on the conclusions, the relationships between surface waves, longitudinal waves, and mechanical properties of materials are established by theoretical derivation. According to the propagation characteristics of surface waves and longitudinal waves, the eccentricity detection scheme of the same side and the concentricity detection scheme of the opposite side are, respectively, designed. The velocities of surface waves and longitudinal waves are measured, considering the thermal expansion coefficient and density changes with temperature. The mechanical properties of materials at different temperatures (25–1000 °C) are successfully calculated, and the experimental results are well in accordance with the reference values. It gives a reliable basis for efficient measurement of mechanical properties of materials at high temperatures.

Thermally tunable Dyakonov surface waves in semiconductor nanowire metamaterials

The development of engineered metamaterials has enabled the fabrication of tunable photonic devices capable of manipulating the characteristics of electromagnetic surface waves. Integration of semiconductors in metamaterials is a proven approach for creating thermally tunable metamaterials through temperature control of the semiconductor carrier density. In this paper, an interface consisting of an isotropic dielectric material as a cover and an indium antimonide (InSb) nanowire metamaterial as a substrate, is theoretically introduced to investigate the propagation conditions of Dyakonov surface waves in terahertz (THz) frequencies. Various temperature-dependent properties of Dyakonov surface waves in such a geometry is studied, including allowed THz regions, angular existence domain, dispersion relation, directionality, localization degree and figure of merit. The proposed configuration due to the presence of significant birefringence in InSb nanowire metamaterial, has potential applications in THz sensing, imaging and spectroscopy.

Experimental and Numerical Study on the Characteristics of Free Surface Waves by the Movement of a Circular Cylinder-Shaped Submerged Body in a Single Fluid Layer

Analyzing the interactions of free surface waves caused by a submerged-body movement is important as a fundamental study of submerged-body motion. In this study, a two-dimensional mini-towing tank was used to tow an underwater body for analyzing the generation and propagation characteristics of free surface waves. The magnitude of the maximum wave height generated by the underwater body motion increased with the body velocity at shallow submerged depths but did not increase further when the generated wave steepness corresponded to a breaking wave condition. Long-period waves were generated in the forward direction as the body moved initially, and then short-period waves were measured when the body moved at a constant velocity. In numerical simulations based on potential flow, the fluid pressure changes caused by the submerged-body motion were implemented, and the maximum wave height was accurately predicted; however, the complex physical phenomena caused by fluid viscosity and wave breaking in the downstream direction were difficult to implement. This research provides a fundamental understanding of the changes in the free surface caused by a moving underwater body.

Simultaneous impact of droplet pairs on solid surfaces

This study investigates the dynamics of the simultaneous impact of two droplets on a dry substrate. We develop a new micro-controlled droplet generator that releases two equally sized water droplets simultaneously on-demand, with no trailing droplets. The impact Weber number, based on impact droplet size and velocity, and the inter-droplet spacing relative to the impact droplet size are varied in the ranges of 54 to 155 and 1.32 to 2.25, respectively, leading to the strong interaction of the spreading lamellae that form a central uprising sheet, which eventually deposits or breaks into tiny droplets. We analyse the impact processes for both deposition and splashing of the uprising sheets. Simultaneous high-speed imaging from two orthogonal views of the droplet impacts quantifies the three-dimensional structure of the sheet morphology, including the temporal evolution of the rim-bounded ‘semilunar’ shape, surface waves, rim corrugations and finger formation, and deposition or splashing of the liquid sheet. The characteristics of the sheet surface waves and the rim instabilities are quantified. Novel scaling is developed for the maximum sheet height, sheet width and thickness, which considers the geometrical constraints and mass balance of the interacting lamellae to describe the temporal evolution of a ‘semilunar’ uprising sheet and is in good agreement with the measurements. The uprising sheet splashing generates larger droplets than those from splashing of single-droplet impacts, and it occurs due to the end-pinching of sheet fingers and at conditions that single-droplet impacts lead only to liquid deposition.

On research of dispersion characteristics of multi-component surface waves from traffic-induced seismic ambient noise

As one of the commonly used sources in passive surface wave exploration, traffic-induced seismic ambient noise is widely used in urban underground velocity structure detection at present. However, characteristics of the dispersion curve extracted from such kind of ambient noise lack systematical research, especially for the multi-component surface wave. Due to the complex character of the real-world underneath structures, dispersion characteristics concluded from real-world traffic-induced seismic ambient noise that is hard to verify. The numerical simulation technique is a good choice for systematical research of characteristics of dispersion curves extracted from multi-component traffic-induced seismic ambient noise. Most of the numerical examples that appeared in the present literature, however, are based on the dispersion-curve-based numerical simulation technique. Hence, most of these can only simulate the vertical component. In this paper, the two-dimensional finite difference method is used to simulate multi-component traffic seismic ambient noise. The characteristics of original traffic noise are analyzed, and the effect of trace intervals on surface wave imaging of different types of traffic-induced noise is studied. Rayleigh wave dispersion energy image is extracted by the passive surface-wave frequency wavenumber transformed method. The differences in Rayleigh-wave dispersion images in traffic noise with different components are analyzed and compared. The results show that Rayleigh wave dispersion energy images appearing different characteristics in different components. The surface wave dispersion information presented by different types of traffic noise is frequency-dependent. The trace spacing also strongly affect the surface-wave dispersion energy images extracted from different types of traffic-induced noise. The numerical results are significant for guiding the traffic-induced seismic noise data acquisition and processing.

Dispersion characteristics of surface wave in SCCS: theoretical analysis, numerical simulation and MASW-based NDT

To fully validate the feasibility of multichannel analysis of surface waves (MASW)-based interfacial debonding detection for steel–concrete composite structures (SCCS), dispersion characteristics of surface waves in SCCS are systematically investigated using theoretical analysis and elaborate 3D numerical simulations. First, the influences of material strength and thickness of concrete core, steel plate thickness on the dispersion figures are analyzed based on the theoretical dispersion characteristic of Rayleigh wave. Scientific layering strategy, including single steel plate, double-layer, and three-layer medium assumptions, is investigated using the theoretical dispersion analysis of Lamb wave. Besides, the dispersion characteristics of surface wave in circular steel pipes are calculated to determine the appropriate theoretical dispersion curves for MASW measurement. Finally, the stress wave propagation processes in SCCSs with various internal structures, including stiffeners, studs, and diaphragms, as well as the debonding width, are simulated using 3D numerical simulation to validate the research finding of theoretical analysis and detectability of MASW-based non-destructive testing on interfacial debonding defects in rectangular and circular concrete-filled steel tubulars. Finally, the dispersion characteristics corresponding to displacement, velocity, and acceleration of surface waves are comparatively discussed. The research findings of this study are the cornerstone of experimental study and essential theoretical support for identifying interfacial debonding and bond-slip damage of SCCS components utilizing MASW method.

Abnormal Waves Observation and Analysis of the Mechanism in the Pearl River Estuary, South China

The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data are critical for achieving a better understanding of waves. In this study, the wave measurements based on a high-precision wave gauge were analyzed and observation data over approximately two years at a sampling frequency of 2 Hz were obtained. The wave system in the Pearl River Estuary was found to deviate from the assumption of a stationary stochastic process similar to that in the open ocean, due to the effects of abnormal waves caused by human activities. Therefore, traditional distribution functions such as Rayleigh and Weibull were not suitable for accurately fitting the main wave parameters (Hs, Tp, etc.), particularly in the tail. Consequently, abnormal wave signals were extracted from all wave sets, and through the comparison and analysis of the wave spectral features, it was determined that these abnormal waves are caused by the ship wakes. The spectral characterization of these waves was performed to determine the characteristics of different ship wake processes. Ship wakes in the Pearl River Estuary are an important part of the wave system, and their wave height is significantly larger than the normal wave. Based on the spectral characteristics of ship wakes, this study proposed some news characteristics of ship wakes in the main channel of the Pearl River Estuary.