Showing papers on "Wave propagation published in 2017"
30 May 2017
208 citations
TL;DR: In this paper, the authors investigated wave propagation in periodic laminates in particular, where both elastic moduli and mass density are modulated in space and time in a wave-like fashion.
Abstract: Research on breaking time-reversal symmetry in wave phenomena is a growing area of interest in the field of phononic crystals and metamaterials aiming to realize one-way propagation devices which have many potential technological applications. Here we investigate wave propagation in phononic crystals, periodic laminates in particular, where both elastic moduli and mass density are modulated in space and time in a wave-like fashion. The modulation introduces a bias which breaks time-reversal symmetry and reciprocity. A full characterization of how the dispersion curve transforms due to wave-like modulations is given in analytical and geometrical terms for both low (subsonic) and high (supersonic) modulation speeds. Theoretical findings are supported by numerical simulations. More specific to low frequencies, the macroscopic constitutive law of 1, 2 and 3D modulated laminates is proven to be of the Willis type with a non-negligible Willis coupling in the strictly scale-separated homogenization limit. The existence of a macroscopic stress-velocity and momentum-strain Willis coupling is in fact directly related to the breaking of reciprocity. Finally, closed form expressions of the macroscopic constitutive parameters are obtained and some elementary yet insightful energy bounds are derived and discussed.
175 citations
TL;DR: In this article, an adaptive hybrid metamaterial that possesses both a negative mass density as well as an extremely tunable stiffness by properly utilizing both the mechanical and electric elements is proposed.
Abstract: Achieving vibration and/or wave attenuation with locally resonant metamaterials has attracted a great deal of attention due to their frequency dependent negative effective mass density Moreover, adaptive phononic crystals with shunted piezoelectric patches have also demonstrated a tunable wave attenuation mechanism by controlling electric circuits to achieve a negative effective stiffness In this paper, we propose an adaptive hybrid metamaterial that possesses both a negative mass density as well as an extremely tunable stiffness by properly utilizing both the mechanical and electric elements A multi-physical analytical model is first developed to investigate and reveal the tunable wave manipulation abilities in terms of both the effective negative mass density and/or bending stiffness of the hybrid metamaterial The programmed flexural wave manipulations, broadband negative refraction and waveguiding are then illustrated through three-dimensional (3D) multi-physical numerical simulations in hybrid metamaterial plates Our numerical results demonstrate that the flexural wave propagation can essentially be switched between “ON/OFF” states by connecting different shunting circuits
168 citations
TL;DR: In this paper, a double double-porosity model is introduced to model the wave effects (attenuation and velocity dispersion), where pores saturated with two different fluids overlap with pores having dissimilar compressibilities.
Abstract: Heterogeneity of rock's fabric can induce heterogeneous distribution of immiscible fluids in natural reservoirs, since the lithological variations (mainly permeability) may affect fluid migration in geological time scales, resulting in patchy saturation of fluids. Therefore, fabric and saturation inhomogeneities both affect wave propagation. To model the wave effects (attenuation and velocity dispersion), we introduce a double double-porosity model, where pores saturated with two different fluids overlap with pores having dissimilar compressibilities. The governing equations are derived by using Hamilton's principle based on the potential energy, kinetic energy, and dissipation functions, and the stiffness coefficients are determined by gedanken experiments, yielding one fast P wave and four slow Biot waves. Three examples are given, namely, muddy siltstones, clean dolomites, and tight sandstones, where fabric heterogeneities at three different spatial scales are analyzed in comparison with experimental data. In muddy siltstones, where intrapore clay and intergranular pores constitute a submicroscopic double-porosity structure, wave anelasticity mainly occurs in the frequency range (104–107 Hz), while in pure dolomites with microscopic heterogeneity of grain contacts and tight sandstones with mesoscopic heterogeneity of less consolidated sands, it occurs at 103–107 Hz and 101–103 Hz (seismic band), respectively. The predicted maximum quality factor of the fast compressional wave for the sandstone is the lowest (approximately 8), and that of the dolomite is the highest. The results of the diffusive slow waves are affected by the strong friction effects between solids and fluids. The model describes wave propagation in patchy-saturated rocks with fabric heterogeneity at different scales, and the relevant theoretical predictions agree well with the experimental data in fully and partially saturated rocks.
160 citations
TL;DR: In this article, the problem formulations of models for three-dimensional weakly nonlinear shallow water waves regime in a stratified shear flow with a free surface were studied and the traveling wave solutions were generated.
Abstract: The problem formulations of models for three-dimensional weakly nonlinear shallow water waves regime in a stratified shear flow with a free surface are studied. Traveling wave solutions are generat...
123 citations
TL;DR: In this article, the wave propagation of generalized thermoelastic medium with voids under the effect of thermal loading due to laser pulse with energy dissipation was studied and a normal mode method was proposed to analyze the problem and obtain numerical solutions for the displacement components, stresses, temperature distribution and the change in the volume fraction field.
Abstract: The aim of this paper is to study the wave propagation of generalized thermoelastic medium with voids under the effect of thermal loading due to laser pulse with energy dissipation. The material is a homogeneous isotropic elastic half-space and heated by a non-Gaussian laser beam with the pulse duration of 0.2 ps. A normal mode method is proposed to analyse the problem and obtain numerical solutions for the displacement components, stresses, temperature distribution and the change in the volume fraction field. The results of the physical quantities have been illustrated graphically by comparison between both types II and III of Green-Naghdi theory for two values of time, as well as with and without void parameters.
115 citations
TL;DR: Modulated metamaterials, which exhibit either non-reciprocal behaviours or non-standard effective mass operators, offer promise for applications in the field of elastic wave control in general and in one-way conversion/amplification in particular.
Abstract: Time-reversal symmetry for elastic wave propagation breaks down in a resonant mass-in-mass lattice whose inner-stiffness is weakly modulated in space and in time in a wave-like fashion. Specifically, one-way wave transmission, conversion and amplification as well as unidirectional wave blocking are demonstrated analytically through an asymptotic analysis based on coupled mode theory and numerically thanks to a series of simulations in harmonic and transient regimes. High-amplitude modulations are then explored in the homogenization limit where a non-standard effective mass operator is recovered and shown to take negative values over unusually large frequency bands. These modulated metamaterials, which exhibit either non-reciprocal behaviours or non-standard effective mass operators, offer promise for applications in the field of elastic wave control in general and in one-way conversion/amplification in particular.
113 citations
TL;DR: In this paper, a piezoelectric sandwich plate is used to simulate the orthotropic visco-Pasternak model and a proportional-derivative (PD) controller is employed to control the phase velocity in the structure.
111 citations
TL;DR: In this article, a nonlocal strain gradient theory was used to capture size effects in wave propagation analysis of compositionally graded smart nanoplates, where a power law function is used to describe the material distribution across the thickness of functionally graded (FG) nanoplate.
101 citations
TL;DR: In this article, the first and higher harmonic components of the resonant fluid response in the gap between two identical fixed rectangular boxes are experimentally investigated in a wave basin and it is shown that for an incident group with appropriate frequency content, the linear gap response may be substantially smaller than the second-harmonic component, which is strongly driven via quadratic coupling of the linear terms from the incident wave and occurs in gap resonant modes.
Abstract: The first- and higher-harmonic components of the resonant fluid response in the gap between two identical fixed rectangular boxes are experimentally investigated in a wave basin. Gap response is excited by transient wave groups (being based on scaled versions of the autocorrelation function of sea state spectra, representing NewWaves, the average shape of large waves in a sea state). Several different wave groups with different maximum surface elevations, spectral peak frequencies and bandwidths are used, while the bilge shape of the boxes and approach angle of the waves are also varied. Unlike a simple regular wave, it is complicated to separate the harmonic components for a transient wave group due to non-linear wave-wave and wave-structure interactions. A four-phase combination methodology is used to separate the first four harmonic components, and this also allows higher-harmonic components to be isolated with simple digital frequency filtering. Harmonic components up to 14th order in the incident wave amplitude have been extracted. It is shown that for an incident group with appropriate frequency content, the linear gap response may be substantially smaller than the second-harmonic component, which is strongly driven via quadratic coupling of the linear terms from the incident wave and occurs in the gap resonant modes. Double frequency excitation may have important practical implications for offshore operations. Fourth and zeroth (long wave) harmonics in the gap are further driven via quadratic coupling of the second-harmonic itself. Linear damping coefficients for the first few modes of the gap resonant response are derived from measured time series using a numerical fit and shown to be higher than those from linear diffraction calculations.
101 citations
TL;DR: In this paper, the dispersion relations and band gaps for the propagation of elastic waves in the undeformed and fully deformed stable configurations were determined using finite element models, and a reduced order model based on a one-dimensional lattice was developed to interpret and explain the emergence of low frequency band gaps in intermediate stable configurations in which some unit cells are undeformed while others are deformed.
TL;DR: In this article, a buoyancy-modified k-ω SST turbulence model was proposed to suppress the turbulence level at the interface between water and air in a numerical wave flume.
TL;DR: In this paper, the influence of joint contact area and spatial geometry of joint surface on the dynamic property of rock joint and wave propagation was investigated using the Split Hopkinson Pressure Bar (SHPB) apparatus.
TL;DR: In this article, it is shown that for specked targets much larger than the wavelength, long-range correlations between the speckles enhance wave propagation control, which is a challenge because of scattering processes.
Abstract: Controlled wave propagation in disordered media is a challenge because of scattering processes. Now it is shown that for speckled targets much larger than the wavelength, long-range correlations between the speckles enhance wave propagation control.
TL;DR: In this article, the exact solitary solutions in generalized form of generalized higher-order nonlinear Schrodinger equation (NLSE) are constructed with the aid of symbolic computation by employing modified extended direct algebraic method.
Abstract: Analysis of short-pulse propagation in positive dispersion media for example in optical fibers and in shallow water, requires assorted high-order derivative terms. The different dynamical features underlying soliton interactions in the generalized higher-order nonlinear Schrodinger equation, which model multimode wave propagation under varied physical situations in nonlinear optics, are studied. In this paper, the new exact solitary solutions in generalized form of generalized higher-order nonlinear Schrodinger equation (NLSE) are constructed with the aid of symbolic computation by employing modified extended direct algebraic method. The complex physical phenomena of generalized higher-order NLSE can be understand from the obtained solutions. The computational work shows that the current method is simple, general, powerful, effective, and wider applicable. Moreover, several new complex higher-order NLSEs that arising in mathematical physics can also be solved by this efficient method.
TL;DR: In this article, the wave propagation of size-dependent functionally graded (FG) nanobeams resting on elastic foundation subjected to axial magnetic field based on the nonlocal strain gradient theory and Euler-Bernoulli beam model was investigated by using an analytical approach.
Abstract: This paper investigates wave propagation of size-dependent functionally graded (FG) nanobeams resting on elastic foundation subjected to axial magnetic field based on the nonlocal strain gradient theory and Euler–Bernoulli beam model by using an analytical approach. The nonlocal beam model has a length scale parameter and captures the size influences. Material properties are spatially graded according to sigmoid distribution. A derivation of the governing equations for the wave propagation analysis of nanoscale S-FGM beams is conducted. Then, the dispersion relations between wave frequency and phase velocity with the wave number is investigated. It is found that wave propagation characteristics of nonlocal S-FGM beams are influenced by various parameters including length scale parameter, material graduation, elastic foundation parameters and magnetic field intensity.
TL;DR: This work demonstrates experimentally not only elastic Rayleigh wave rainbow trapping, by taking advantage of a stop-band for surface waves, but also selective mode conversion of surface Rayleigh waves to shear waves.
Abstract: Recent years have heralded the introduction of metasurfaces that advantageously combine the vision of sub-wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. An important topic within metasurfaces is the tailored rainbow trapping and selective spatial frequency separation of electromagnetic and acoustic waves using graded metasurfaces. This frequency dependent trapping and spatial frequency segregation has implications for energy concentrators and associated energy harvesting, sensing and wave filtering techniques. Different demonstrations of acoustic and electromagnetic rainbow devices have been performed, however not for deep elastic substrates that support both shear and compressional waves, together with surface Rayleigh waves; these allow not only for Rayleigh wave rainbow effects to exist but also for mode conversion from surface into shear waves. Here we demonstrate experimentally not only elastic Rayleigh wave rainbow trapping, by taking advantage of a stop-band for surface waves, but also selective mode conversion of surface Rayleigh waves to shear waves. These experiments performed at ultrasonic frequencies, in the range of 400–600 kHz, are complemented by time domain numerical simulations. The metasurfaces we design are not limited to guided ultrasonic waves and are a general phenomenon in elastic waves that can be translated across scales.
TL;DR: In this article, a general bi-Helmholtz nonlocal strain-gradient elasticity model is developed for wave dispersion analysis of porous double-nanobeam systems in thermal environments.
TL;DR: In this paper, the propagation of time harmonic plane waves is investigated in an infinite nonlocal elastic solid material with voids, and the governing relations and equations are derived for nonlinear elastic solid with void.
Abstract: In this paper, the governing relations and equations are derived for nonlocal elastic solid with voids. The propagation of time harmonic plane waves is investigated in an infinite nonlocal elastic solid material with voids. It has been found that three basic waves consisting of two sets of coupled longitudinal waves and one independent transverse wave may travel with distinct speeds. The sets of coupled waves are found to be dispersive, attenuating and influenced by the presence of voids and nonlocality parameters in the medium. The transverse wave is dispersive but non-attenuating, influenced by the nonlocality and independent of void parameters. Furthermore, the transverse wave is found to face critical frequency, while the coupled waves may face critical frequencies conditionally. Beyond each critical frequency, the respective wave is no more a propagating wave. Reflection phenomenon of an incident coupled longitudinal waves from stress-free boundary surface of a nonlocal elastic solid half-space with voids has also been studied. Using appropriate boundary conditions, the formulae for various reflection coefficients and their respective energy ratios are presented. For a particular model, the effects of non-locality and dissipation parameter (
$\tau $
) have been depicted on phase speeds and attenuation coefficients of propagating waves. The effect of nonlocality on reflection coefficients has also been observed and shown graphically.
TL;DR: In this article, a new resonator with high-static-low-dynamic stiffness (HSLDS) was proposed to further lower the band gaps of flexural wave propagation in local resonance (LR) beams.
Abstract: Periodic structures are effective in attenuating waves in low frequency range at local resonance (LR) conditions, but it is still a challenge to achieve this in very low frequency range. The main original contribution of this paper is to further lower the band gaps of flexural wave propagation in LR beams by developing a new resonator with high-static-low-dynamic stiffness (HSLDS). The proposed resonator is designed by combining a vertical spring with two oblique springs that provide negative stiffness in the vertical direction, and thus the stiffness of the vertical spring can be counteracted effectively by the negative-stiffness (NS) mechanisms. The band structures of HSLDS-LR beams, obtained by the transfer matrix method and verified by numerical simulations, demonstrate that band gaps can be shifted to much lower frequency than that of conventional LR beams. Most importantly, the band gaps can be assigned to desired locations by adjusting only the stiffness of the oblique springs. For wave attenuation...
TL;DR: In this article, a unit cell method including damping is used to analyse the complex dispersion curves of a locally resonant metamaterial design, and the influence on the dispersion curve of damping in resonator and host structure is discussed.
TL;DR: In this paper, the effects of nonlocal and material length scale parameters, wave number, fluid velocity and stiffness of elastic foundation are more considerable in the nonlocal strain gradient theory than in classical theory.
Abstract: In this paper, wave propagation in fluid-conveying double-walled carbon nanotube (DWCNT) was investigated by using the nonlocal strain gradient theory. In so doing, the shear deformable shell theory was used, taking into consideration nonlocal and material length scale parameters. The effect of van der Waals force between the two intended walls and the DWCNT surroundings was modeled as Winkler foundation. The classical governing equations were derived from Hamilton’s principle. Results were validated by comparing them to the results of the references obtained through molecular dynamic method, and a remarkable consistency was found between the results. According to the findings, the effects of nonlocal and material length scale parameters, wave number, fluid velocity and stiffness of elastic foundation are more considerable in the nonlocal strain gradient theory than in classical theory.
TL;DR: It is shown that these intensity variations can be entirely suppressed by adding disorder-specific gain and loss components to the medium and the resulting constant-intensity waves in such non-Hermitian scattering landscapes are free of any backscattering and feature perfect transmission through the disorder.
Abstract: A fundamental manifestation of wave scattering in a disordered medium is the highly complex intensity pattern the waves acquire due to multi-path interference. Here we show that these intensity variations can be entirely suppressed by adding disorder-specific gain and loss components to the medium. The resulting constant-intensity waves in such non-Hermitian scattering landscapes are free of any backscattering and feature perfect transmission through the disorder. An experimental demonstration of these unique wave states is envisioned based on spatially modulated pump beams that can flexibly control the gain and loss components in an active medium. Constant-intensity waves that can travel through a disordered medium without being scattered or reflected are being theoretically predicted. The analysis of Konstantinos Makris of the University of Crete, Greece, and co-workers from Austria and the United States suggests that such constant-intensity waves can form in a general disordered medium provided a suitable distribution of the imaginary part of the medium’s refractive index is achieved by spatially varying the gain and loss of the medium appropriately. In other words, adding a judiciously selected gain-and-loss distribution to a disordered medium causes waves to lose all of their internal intensity variations so that they travel through the disorder without being back-reflected. This behaviour should be experimentally confirmable by spatially modulating the pump beams in an active medium to create the desired gain-loss profile.
TL;DR: In this article, a wave-in-ice model calibration study is presented, where wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region.
Abstract: This paper presents a wave-in-ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region. Wavenumbers are measured in one of these experiments. Forcing parameters are obtained from simultaneous in-situ and remote sensing observations, as well as forecast/hindcast models. Cases from three wave experiments are used to calibrate a viscoelastic model for wave attenuation/dispersion in ice cover. The calibration is done by minimizing the difference between modeled and measured complex wavenumber, using a multi-objective genetic algorithm. The calibrated results are validated using two methods. One is to directly apply the calibrated viscoelastic parameters to one of the wave experiments not used in the calibration and then compare the attenuation from the model with measured data. The other is to use the calibrated viscoelastic model in WAVEWATCH III® over the entire western Beaufort Sea and then compare the wave spectra at two remote sites not used in the calibration. Both validations show reasonable agreement between the model and the measured data. The completed viscoelastic model is believed to be applicable to the fall marginal ice zone dominated by pancake ice.
TL;DR: It is shown that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition.
Abstract: We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.
TL;DR: In this article, a local periodical forcing is applied on the media to induce continuous target wave in the improved cardiac model, which the effect of electromagnetic induction is considered by using magnetic flux, then external electromagnetic radiation is imposed on media.
Abstract: Continuous wave emitting from sinus node of the heart plays an important role in wave propagating among cardiac tissue, while the heart beating can be terminated when the target wave is broken into turbulent states by electromagnetic radiation. In this investigation, local periodical forcing is applied on the media to induce continuous target wave in the improved cardiac model, which the effect of electromagnetic induction is considered by using magnetic flux, then external electromagnetic radiation is imposed on the media. It is found that target wave propagation can be blocked to stand in a local area and the excitability of media is suppressed to approach quiescent but homogeneous state when electromagnetic radiation is imposed on the media. The sampled time series for membrane potentials decrease to quiescent state due to the electromagnetic radiation. It could accounts for the mechanism of abnormality in heart failure exposed to continuous electromagnetic field.
TL;DR: In this paper, a wave vector analysis is conducted that enables selection of primary waves traveling in any direction that generate phase matched secondary waves, and the authors have tabulated many sets of primary wave and secondary wave sets.
Abstract: The extraordinary sensitivity of nonlinear ultrasonic waves to the early stages of material degradation makes them excellent candidates for nondestructive material characterization. However, distinguishing weak material nonlinearity from instrumentation nonlinearity remains problematic for second harmonic generation approaches. A solution to this problem is to mix waves having different frequencies and to let their mutual interaction generate sum and difference harmonics at frequencies far from those of the instrumentation. Mixing of bulk waves and surface waves has been researched for some time, but mixing of guided waves has not yet been investigated in depth. A unique aspect of guided waves is their dispersive nature, which means we need to assure that a wave can propagate at the sum or difference frequency. A wave vector analysis is conducted that enables selection of primary waves traveling in any direction that generate phase matched secondary waves. We have tabulated many sets of primary waves and ...
TL;DR: In this paper, a general bi-Helmholtz nonlocal strain-gradient elasticity model is developed for wave dispersion analysis of porous double-nanobeam systems on elastic substrate.
TL;DR: In this paper, a two-dimensional micro-channel model for peristaltic transport of aqueous nanofluids in a bio-mimetic pumping system is presented.
TL;DR: In this article, the dispersion properties of a state-based linear peridynamic solid model were investigated and the role of the horizon was investigated, where the authors showed how the influence function can be used to minimize wave dispersion at a fixed lattice spacing and demonstrate it qualitatively by wave propagation analysis in one-and two-dimensional models of elastic solids.
Abstract: Peridynamics is a nonlocal continuum model which offers benefits over classical continuum models in cases, where discontinuities, such as cracks, are present in the deformation field. However, the nonlocal characteristics of peridynamics leads to a dispersive dynamic response of the medium. In this study we focus on the dispersion properties of a state-based linear peridynamic solid model and specifically investigate the role of the peridynamic horizon. We derive the dispersion relation for one, two and three dimensional cases and investigate the effect of horizon size, mesh size (lattice spacing) and the influence function on the dispersion properties. We show how the influence function can be used to minimize wave dispersion at a fixed lattice spacing and demonstrate it qualitatively by wave propagation analysis in one- and two-dimensional models of elastic solids. As a main contribution of this paper, we propose to associate peridynamic non-locality expressed by the horizon with a characteristic length scale related to the material microstructure. To this end, the dispersion curves obtained from peridynamics are compared with experimental data for two kinds of sandstone.