Dispersive Wave Propagation Research Articles

New wave behaviors of the (3+1)-dimensional Date-Jimbo-Kashiwara-Miwa equation

In this study, the (3+1)-dimensional Date-Jimbo-Kashiwara-Miwa equation that indicated the propagation of nonlinear dispersive waves in inhomogeneous media is given for consideration. The generalized exponential rational function method is used to seek some new exact solutions for the considered equation. The three-dimensional surfaces and two-dimensional graphs of the obtained solutions are plotted by choosing the appropriate values of the involving free parameters.

Dispersive wave propagation of the nonlinear Sasa-Satsuma dynamical system with computational and analytical soliton solutions

The Sasa-Satsuma equation on a continuous background describes a nonlinear fiber system with higher-order effects including the third-order dispersion and Kerr dispersion. The Sasa-Satsuma equations describe the simultaneous propagation of two ultrashort pulses in the birefringent or two-mode fiber with the third-order dispersion, self-steepening, and stimulated Raman in scattering effects, and govern the propagation of ultra-fast pulses in optical fiber transmission systems. We consider the Sasa-Satsuma equation, which is one of the integrable extensions of the nonlinear Schrödinger equations. We find the functional integral and the Lagrangian of this model. We derived the computational and analytical soliton solutions of the nonlinear Sasa-Satsuma dynamical system. We discuss the stability analysis for our solutions.

Exploring wave propagation in heterogeneous metastructures using the relaxed micromorphic model

Metamaterials are artificial structures that can manipulate and control sound waves in ways not possible with conventional materials. While much effort has been undertaken to widen the bandgaps produced by these materials through design of heterogeneities within unit cells, comparatively little work has considered the effect of engineering heterogeneities at the structural scale by combining different types of unit cells. In this paper, we use the relaxed micromorphic model to study wave propagation in heterogeneous metastructures composed of different unit cells. We first establish the efficacy of the relaxed micromorphic model for capturing the salient characteristics of dispersive wave propagation through comparisons with direct numerical simulations for two classes of metamaterial unit cells: namely phononic crystals and locally resonant metamaterials. We then use this model to demonstrate how spatially arranging multiple unit cells into metastructures can lead to tailored and unique properties such as spatially-dependent broadband wave attenuation, rainbow trapping, and pulse shaping. In the case of the broadband wave attenuation application, we show that by building layered metastructures from different metamaterial unit cells, we can slow down or stop wave packets in an enlarged frequency range, while letting other frequencies through. In the case of the rainbow-trapping application, we show that spatial arrangements of different unit cells can be designed to progressively slow down and eventually stop waves with different frequencies at different spatial locations. Finally, in the case of the pulse-shaping application, our results show that heterogeneous metastructures can be designed to tailor the spatial profile of a propagating wave packet. Collectively, these results show the versatility of the relaxed micromorphic model for effectively and accurately simulating wave propagation in heterogeneous metastructures, and how this model can be used to design heterogeneous metastructures with tailored wave propagation functionalities.

Construction of Lump and optical solitons solutions for (3 + 1) model for the propagation of nonlinear dispersive waves in inhomogeneous media

Our work aims to investigate new solutions for the (3 + 1)-dimensional Extended Date–Jimbo–Kashiwara–Miwa Equation which characterize the physical phenomena owing to the inhomogeneities of media. By using the Hirota—method with the aid of a quadratic test function, we derived a new Lump—soliton solution that localized in all directions in space and time. A class of 1-soliton solution and more-soliton solution are explored using the improved tanh–coth method and the improved tan–cot method. The sequel in these solutions demonstrate a valuation of physical phenomenon. Two, three-dimensional, contour and density plots are presented to illustrate the behaviors of the solitons.

Scattering of Matter Wave Solitons on Localized Potentials

We study the reflection and transmission properties of matter wave solitons impinging on localized scattering potentials in one spatial dimension. By mean field analysis we identify regimes where the solitons behave more like waves or more like particles as a result of the interplay between the dispersive wave propagation and the attractive interactions between the atoms. For a bright soliton propagating together with a dark soliton void in a two-species Bose-Einstein condensate, we find different reflection and transmission properties of the dark and the bright components.

Stochastic Wave\u2013Current Interaction in Thermal Shallow Water Dynamics

Holm (Proc R Soc A Math Phys Eng Sci 471(2176):20140963, 2015) introduced a variational framework for stochastically parametrising unresolved scales of hydrodynamic motion. This variational framework preserves fundamental features of fluid dynamics, such as Kelvin’s circulation theorem, while also allowing for dispersive nonlinear wave propagation, both within a stratified fluid and at its free surface. The present paper combines asymptotic expansions and vertical averaging with the stochastic variational framework to formulate a new approach for developing stochastic parametrisation schemes for nonlinear waves in fluid dynamics. The approach is applied to two sequences of shallow water models which descend from Euler’s three-dimensional fluid equations with rotation and stratification under approximation by asymptotic expansions and vertical averaging. In the entire family of nonlinear stochastic wave–current interaction equations derived here using this approach, Kelvin’s circulation theorem reveals a barotropic mechanism for wave generation of horizontal circulation or convection (cyclogenesis) which is activated whenever the gradients of wave elevation and/or topography are not aligned with the gradient of the vertically averaged buoyancy.

Rational solutions, and the interaction solutions to the (2 + 1)-dimensional time-dependent Date–Jimbo–Kashiwara–Miwa equation

In this work, the Date–Jimbo–Kashiwara–Miwa (DJKM) equation include time-dependent in -dimensions that characterize the propagation of nonlinear dispersive waves in inhomogeneous media is studied. We construct rational solutions and the interaction physical phenomena between rational solution and multi-soliton wave to the time-dependent DJKM equation. The multi-soliton solutions are revealed by using the Hirota simple method, and then via the long-wave method, the M-lump solutions for two types of time-dependent are derived. Moreover, the interaction phenomena between rational solution and single-, double-soliton solutions are studied.

Galerkin finite element methods for the numerical solution of two classical-Boussinesq type systems over variable bottom topography

We consider two ‘Classical’ Boussinesq type systems modelling two-way propagation of long surface waves in a finite channel with variable bottom topography. Both systems are derived from the 1-d Serre–Green–Naghdi (SGN) system; one of them is valid for stronger bottom variations, and coincides with Peregrine’s system, and the other is valid for smaller bottom variations. We discretize in the spatial variable simple initial–boundary-value problems (ibvp’s) for both systems using standard Galerkin-finite element methods and prove L2 error estimates for the ensuing semidiscrete approximations. We couple the schemes with the 4th order-accurate, explicit, classical Runge–Kutta time-stepping procedure and use the resulting fully discrete methods in numerical simulations of dispersive wave propagation over variable bottoms with several kinds of boundary conditions, including absorbing ones. We describe in detail the changes that solitary waves undergo when evolving under each system over a variety of variable-bottom environments. We assess the efficacy of both systems in approximating these flows by comparing the results of their simulations with each other, with simulations of the SGN-system, and with available experimental data from the literature.

Propagation of ultrasonic guided waves in plant leaves

In this work, dispersive wave propagation in plant leaves is studied using a long distance laser-based ultrasonic method. Guided waves traveling through and along the midrib, as well as in the lamina, are measured and analyzed via wave attenuation, characteristic diagram and dispersion curves. Additionally, an estimation of the leaf elastic properties using the Rayleigh–Lamb model, supported by thickness-resonance frequency constraints, is proposed. This study paves the way for the development of acoustic fingerprints for the identification of leaves and their non-invasive and fairly non-destructive mechanical characterization, which is highly related to the plant hydraulics and photosynthetic activity.

Harmonic wideband simultaneous dual-frequency MR Elastography.

Magnetic resonance elastography (MRE) is used to non-invasively quantify viscoelastic properties of tissues based on the measurement of propagation characteristics of shear waves. Because some of these viscoelastic parameters show a frequency dependence, multifrequency analysis allows us to measure the wave propagation dispersion, leading to a better characterization of tissue properties. Conventionally, motion encoding gradients (MEGs) oscillating at the same frequency as the mechanical excitation encode motion. Hence, multifrequency data is usually obtained by sequentially repeating monochromatic wave excitations experiments at different frequencies. The result is that the total acquisition time is multiplied by a factor corresponding to the number of repetitions of monofrequency experiments, which is a major limitation of multifrequency MRE. In order to make it more accessible, a novel single-shot harmonic wideband dual-frequency MRE method is proposed. Two superposed shear waves of different frequencies are simultaneously generated and propagate in a sample. Trapezoidal oscillating MEGs are used to encode mechanical vibrations having frequencies that are an odd multiple of the MEG frequency. The number of phase offsets is optimized to reduce the acquisition time. For this purpose, a sampling method not respecting the Shannon theorem is used to produce a controlled temporal aliasing that allows us to encode both frequencies without any additional examination time. Phantom experiments were run to compare conventional monofrequency MRE with the single-shot dual-frequency MRE method and showed excellent agreement between the reconstructed shear storage moduli G'. In addition, dual-frequency MRE yielded an increased signal-to-noise ratio compared with conventional monofrequency MRE acquisitions when encoding the high frequency component. The novel proposed multifrequency MRE method could be applied to simultaneously acquire more than two frequency components, reducing examination time. Further studies are needed to confirm its applicability in preclinical and clinical models.

Dispersion, spurious reflections and spurious bifurcations of flexural waves

This paper investigates the wave propagation dispersion, spurious reflection and spurious bifurcation of flexural waves that occur in the numerical integration of the wave equation. To this end, the classic cubic beam finite elements of two nodes with a consistent mass matrix for integration in space and the Newmark average acceleration integration method of a single step for integration in time are considered. The resultant system of the difference equations is then analytically integrated in non-finite terms (numerical wave solution) using complex notation. Numerical results reveal that even for a refined mesh the dispersion and spurious reflections are quite high in comparison with numerical integration of the scalar wave.

Interaction phenomena among lump, periodic and kink wave solutions to a (3 + 1)-dimensional Sharma-Tasso-Olver-like equation

In this article, we consider a (3 + 1)-dimensional Sharma–Tasso–Olver-like (STOL) model describing dynamical propagation of nonlinear dispersive waves in inhomogeneous media. Applying Hirota's bilinear technique and a trial function, we explore nonlinear dynamical properties of basic solutions to the STOL model. We find that the fission fusion pattern occurs in the collision between the lump and kink waves, the collision between the lump and periodic waves, and the collision among the lump, kink and periodic waves, which is a novel fascinating collision pattern. We also observe that a large value of the coefficient in the periodic function produces a hybrid lump wave by fission in the collision solution. To better understand the dynamic properties of the obtained collision solutions, we plot a number of 3D and contour diagrams by choosing suitable parametric values with the aid of the computational software Maple 18.

Finite element implementation of a multi-scale dynamic piezomagnetic continuum model

A gradient-enriched dynamic piezomagnetic model is presented. The gradient enrichment introduces a number of microstructural terms in the model that allow the description of dispersive wave propagation. A novel derivation based on homogenisation principles is shown to lead to a multi-scale formulation in which the micro-scale displacements and magnetic potential are included alongside the macro-scale displacements and magnetic potential. The multi-scale formulation of the model has the significant advantage that all higher-order terms are rewritten as second-order spatial derivatives. As a consequence, a standard C0-continuous finite element discretisation can be used. Details of the finite element implementation are given. A series of one and two-dimensional examples shows the effectiveness of the model to describe dispersive wave propagation and remove singularities in a coupled elasto-magnetic context.

Role of higher-order inertia in modulating elastic wave dispersion in materials with granular microstructure

(Meta-) materials with granular microstructures exhibit nonlinear dispersive wave propagation, which is typically attributed to the presence of a microstructure. However, this behavior can arise from two additional sources in a linear non-dissipative system – the grain-scale or micromechanical characteristics and the grain-scale or micro-inertial characteristics. The microstructure, the grain-scale mechanical and the grain-scale inertial properties in combination may be designated as micro-mechano-morphology. From a continuum modeling viewpoint, the observed dispersion behavior that accounts for micro-mechano-morphology of materials with granular microstructures can be described using a granular micromechanics based micromorphic model (Nejadsadeghi and Misra 2019b, Misra and Poorsolhjouy 2016). Following the approach outlined in these works, we elaborate on the effect of micro-scale inertia upon the wave propagation behavior. The work is motivated by the observation of negative group velocity of optical waves seen in simulations using discrete models of granular media. We show that higher-order inertia is necessary for describing this phenomena using continuum models. We further show that this phenomena can be modulated by micro-scale mass density distributions, thus affecting the widths of potential frequency band-gaps, including the negative group velocity of the acoustic branch.

Lie symmetry analysis, optimal system, and generalized group invariant solutions of the (2 + 1)‐dimensional Date–Jimbo–Kashiwara–Miwa equation

In this work, Lie group theoretic method is used to carry out the similarity reduction and solitary wave solutions of (2 + 1)‐dimensional Date–Jimbo–Kashiwara–Miwa (DJKM) equation. The equation describes the propagation of nonlinear dispersive waves in inhomogeneous media. Under the invariance property of Lie groups, the infinitesimal generators for the governing equation have been obtained. Thereafter, commutator table, adjoint table, invariant functions, and one‐dimensional optimal system of subalgebras are derived by using Lie point symmetries. The symmetry reductions and some group invariant solutions of the DJKM equation are obtained based on some subalgebras. The obtained solutions are new and more general than the rest while known results reported in the literature. In order to show the physical affirmation of the results, the obtained solutions are supplemented through numerical simulation. Thus, the solitary wave, doubly soliton, multi soliton, and dark soliton profiles of the solutions are traced to make this research physically meaningful.

An efficient computational technique for time-fractional modified Degasperis-Procesi equation arising in propagation of nonlinear dispersive waves

In this paper, an efficient hybrid numerical scheme which is based on a joint venture of the q-homotopy analysis method and Sumudu transform is applied to investigate the time-fractional modified Degasperis-Procesi (DP) equation. The present study considers the Caputo fractional derivative. The fractional order modified DP model is very important and plays a great role in study of ocean engineering and science. The proposed scheme provides a beautiful opportunity for proper selection of the auxiliary parameter ℏ and the asymptotic parameter ρ ( ≥ 1) to handle mainly the differential equations of nonlinear nature. The offered scheme produces the solution in the shape of a convergent series in a large admissible domain which is helpful to regulate the region of convergence of a series solution. The proposed work computes the approximate analytical solution of the fractional modified DP equation systematically and also presents graphically the variation of the obtained solution for diverse values of the fractional parameter β.

Propagation of Rayleigh waves at the boundary of an orthotropic elastic solid: Influence of initial stress and gravity

Propagation of harmonic plane waves is considered in an orthotropic elastic medium in the presence of initial stress and gravity. Roots of a quadratic equation define the propagation of one quasi-longitudinal wave and one quasi-transverse wave in a symmetry plane in this medium. These two waves are coupled in the identical phase to define the propagation of Rayleigh waves at the boundary of the medium. Two conditions at the stress-free boundary translate into a complex frequency equation, which explains the dispersive behavior of this Rayleigh wave. For the presence of radical terms, this complex equation is rationalized into a real algebraic equation. Only one root of this algebraic equation satisfies the mother frequency equation and hence represents the propagation of dispersive Rayleigh waves at the boundary of the orthotropic solid. The influence of initial stress and gravity on velocity and polarization of Rayleigh waves is observed through a numerical example.

Modulation theory and resonant regimes for dispersive shock waves in nematic liquid crystals

A full analysis of all regimes for optical dispersive shock wave (DSW) propagation in nematic liquid crystals is undertaken. These dispersive shock waves are generated from step initial conditions for the optical field and are resonant in that linear diffractive waves are in resonance with the DSW, resulting in a resonant linear wavetrain propagating ahead of it. It is found that there are six regimes, which are distinct and require different solution methods. In previous studies, the same solution method was used for all regimes, which does not yield solutions in full agreement with numerical solutions. Indeed, the standard DSW structure disappears for sufficiently large initial jumps. Asymptotic theory, approximate methods or Whitham modulation theory are used to find solutions for these resonant dispersive shock waves in a given regime. The solutions are found to be in excellent agreement with numerical solutions of the nematic equations in all regimes. It is found that for small initial jumps, the resonant wavetrain is unstable, but that it stabilises above a critical jump height. It is additionally found that the DSW is unstable, except for small jump heights for which there is no resonance and large jump heights for which there is no standard DSW structure.

Asymptotic analysis of dispersive tsunami from a slender fault

An approximate theory is developed for the two-dimensional propagation of tsunami emanated from a slender fault of fine length. Assuming significant contrasts between the sea depth, fault width, fault length and the bathymetric length scales, we invoke parabolic approximation to deduce a linear Kademtsev-Petviashivili (K-P) equation governing the two-dimensional propagation of dispersive long waves over great distances. Analytical techniques are employed to explore the far-field radiation in the forward and spanwise directions in a sea of constant depth. The solution can be used as a convenient input for predicting local variations of wave scattering and possibly breaking along a coast.

Construction of abundant solutions of the (2+1)-dimensional time-dependent Date–Jimbo–Kashiwara–Miwa equation

Investigated in the current paper is the time-dependent Date–Jimbo–Kashiwara–Miwa equation in (2+1)-dimensions which works as a model for describing the propagation of nonlinear dispersive waves in inhomogeneous media. By implementing the homoclinic test method, the breather-kink wave solution to the considered equation is first generated. Then, based on the resulting solution and a parameter transformation, the double-solitary wave solution is obtained. Finally, the rogue wave emerges by taking a limit behavior. Meanwhile, some graphs are made to shed light on the structural characteristics.