Green Naghdi Research Articles

Band structure analysis of Green-Naghdi-based thermoelastic wave propagation in cylindrical phononic crystals with energy dissipation using a meshless collocation method

In this paper, a meshless collocation method based on the generalized finite difference (GFD) method is employed for the band structure analysis of thermoelastic waves propagating in the cylindrical phononic crystal (PC). The Green-Naghdi (GN) theory of the generalized coupled thermoelasticity with energy dissipation and the Bloch's theorem are adopted to compute the dispersion relation of thermoelastic waves. The proposed GFD-based meshless collocation method is used to predict the frequency range of the band-gaps and to analyze the effects of the material parameters and the thickness of each layer (sub-cylinder) in a unit-cell on the band-gap property of thermoelastic waves propagating in the cylindrical PCs. The effects of the variations in the layer thicknesses in each unit-cell on the thermoelastic wave band structures are studied in detail. Also, the influences of the key material parameters on the frequency band structures of the thermoelastic waves are investigated. It will be shown that the dimensionless speed of the thermal wave influences the band-gaps more remarkably than other dimensionless parameters such as the dimensionless speeds of the purely elastic dilatational and shear waves, the damping coefficient and the thermoelastic coupling parameter.

Thermoelastic diffusion of a solid cylinder in the context of modified Green–Naghdi models

The generalized thermoelastic diffusion model is introduced and applied to an isotropic cylinder. The cylinder is under the effect of thermal flux and chemical potential. Some modifications are made to the Green and Naghdi model. Creative multi-phase-lag models with and without energy dissipation are proposed to discuss the thermoelastic diffusion of the circular solid cylinders. The analytical solutions of thermoelastic diffusion governing equations of the solid cylinders have been deduced. Comparing examples are presented between the simple and refined Green–Naghdi of types II and III models. The validity of results is worthy and benchmark outcomes are accounted for to help different specialists in their future examinations.

Modified Moore–Gibson–Thompson photo-thermoelastic model for a rotating semiconductor half-space subjected to a magnetic field

This paper focuses on studying thermal, elastic and coupled plasma waves, in the sense of a photo-thermal process transport within an infinite semiconductor medium. In order to study photo-thermal interactions in two-dimensional semiconducting materials, a new mathematical model based on the Moore–Gibson–Thompson equation (MGTE) is implemented. The MGTE model involving the Green–Naghdi model of type III as well as the heat transport equation proposed by Lord and Shulman. We consider the semi-conductor half-space is rotated at a uniform angular speed and magnetized. The analysis of the distribution of thermophysical fields has been extracted by a normal mode method, represented graphically and discussed. The results predicted by the new and improved model have been compared with the generalized and classic ones. In addition, all field quantities have been examined for effects of rotation, a lifetime of the photo-generated, and the applied magnetic field.

Well-posedness for thermo-electro-viscoelasticity of Green–Naghdi type

We study the linear theory of thermo-electro-viscoelasticity of Green–Naghdi type for the case of a one-dimensional body. For the corresponding mathematical model, we prove a uniqueness theorem of the solution to the mixed boundary-initial-value problem by means of the Laplace transform after rewriting the constitutive equations in an appropriate form. Moreover, we derive a result of continuous dependence upon the supply terms.

Solution of Moore–Gibson–Thompson Equation of an Unbounded Medium with a Cylindrical Hole

In the current article, in the presence of thermal and diffusion processes, the equations governing elastic materials through thermodiffusion are obtained. The Moore–Gibson–Thompson (MGT) equation modifies and defines the equations for thermal conduction and mass diffusion that occur in solids. This modification is based on adding heat and diffusion relaxation times in the Green–Naghdi Type III (GN-III) models. In an unbounded medium with a cylindrical hole, the built model has been applied to examine the influence of the coupling between temperature and mass diffusion and responses. At constant concentration as well as intermittent and decaying varying heat, the surrounding cavity surface is traction-free and is filled slowly. Laplace transform and Laplace inversion techniques are applied to obtain the solutions of the studied field variables. In order to explore thermal diffusion analysis and find closed solutions, a suitable numerical approximation technique has been used. Comparisons are made between the results obtained with the results of the corresponding previous models. Additionally, to explain and realize the presented model, tables and figures for various physical fields are presented.

Gaussian thermal shock-induced thermoelastic wave propagation in an FG multilayer hybrid nanocomposite cylinder reinforced by GPLs and CNTs

In this paper, a new modified micromechanical model is proposed to obtain the mechanical and thermal properties of a reinforced functionally graded (FG) multilayer hybrid nanocomposite cylinder for thermoelastic wave propagation analysis with energy dissipation using Green–Naghdi theory. The FG multilayer hybrid nanocomposite cylinder is assumed to be under Gaussian thermal shock loading and also it is reinforced by graphene platelets (GPLs) and carbon nanotubes (CNTs). The cylinder is assumed to be made of multi-layers (sub-cylinders), and each layer is reinforced by a uniform distribution of GPLs and CNTs. A modified micromechanical model is proposed to calculate the thermo-mechanical properties with nonlinear grading patterns of the GPLs and CNTs along the radial direction of the cylinder. The nonlinear grading patterns of the GPLs and CNTs distributions along the radial direction of the whole cylinder can be created using a suitable arrangement of the layers (sub-cylinders). An effective meshless collocation method based on the generalized finite difference (GFD) method and the Newmark method are employed to solve the coupled governing equations of the GN-based coupled thermoelasticity analysis. The effects of the key parameters such as the weight fraction of the GPLs and CNTs and volume fraction index on the thermoelastic wave propagations and dynamic behaviors of the field variables are studied in detail. Also, the effects of the reinforcement by GPLs and/or CNTs in a hybrid nanocomposite on the transient behaviors of cylinder in both temperature and displacement fields are compared. The accuracy and stability of the presented meshless method and also the proposed new modified micromechanical model is verified by the published reference data.

An extension of the Boussinesq-type models to weakly compressible flows

An extension of the Boussinesq-type models to weakly compressible flows is derived in the fully nonlinear case. The dispersive properties are consistent with the linear theory of compressible fluids at the long-wave limit. The particular case of a vanishing Mach number gives a quasi-incompressible model, intended for coastal wave simulations, which is a hyperbolic version of the Serre–Green–Naghdi equations, with a new treatment of the bathymetric terms. Both the compressible and quasi-incompressible models are hyperbolic four-equation models on an arbitrary bathymetry, with an exact equation of energy conservation. In addition, these models are extended to hyperbolic and fully nonlinear five-equation versions with improved dispersive properties. A remarkable property of the quasi-incompressible model with improved dispersive properties is that it is possible to decrease significantly the sound velocity, and thus the computational time, with the same accuracy or even slightly better. The numerical results show good agreement of the quasi-incompressible model with experimental data and the capability of the compressible model to calculate the decrease of tsunami velocity due to compressible effects.

Decay of quasi-static porous-thermo-elastic waves

We study the behavior in time of the solutions to several systems of equations for porous-thermo-elastic problems when one of the variables is considered to be quasi-static or, in other words, whose second time derivative can be neglected. We analyze three different situations using the classical Fourier law and also the type II or type III Green–Naghdi heat conduction models.

Asymptotic Shallow Models Arising in Magnetohydrodynamics

In this paper, we derive new shallow asymptotic models for the free boundary plasma-vacuum problem governed by the magnetohydrodynamic equations which are vital when describing large-scale processes in flows of astrophysical plasma. More precisely, we present the magnetic analogue of the 2D Green–Naghdi equations for water waves under a weak magnetic pressure assumption in the presence of weakly sheared vorticity and magnetic currents. Our method is inspired by ideas for hydrodynamic flows developed in Castro and Lannes (2014) to reduce the three-dimensional dynamics of the vorticity and current to a finite cascade of two dimensional equations which can be closed at the precision of the model.

Variational generalization of the Green–Naghdi and Whitham equations for fluid sloshing in three-dimensional rotating and translating coordinates

This paper derives an averaged Lagrangian functional for dynamic coupling between rigid-body motion and its interior shallow-water sloshing in three-dimensional rotating and translating coordinates; with a time-dependent rotation vector. A new set of variational shallow-water equations (SWEs) and generalized Green–Naghdi equations for the interior fluid sloshing with 3-D rotation vector and translations, and also the equations of motion for the linear momentum and angular momentum of the rigid-body containing shallow water, are derived from the averaged Lagrangian functional, which describes a columnar motion, by using Hamilton’s principle and the Euler–Poincaré variational framework. The generalized Green–Naghdi equations have a form of potential vorticity (PV) conservation, which can be obtained from the particle-relabelling symmetry, and is a combination of the PV derived by Miles and Salmon (1985) and the PV derived by Dellar and Salmon (2005) for geophysical fluid dynamics problems, where the rotation vector varies spatially. By applying the assumption of zero-potential-vorticity flow to the averaged Lagrangian functional, a new set of Boussinesq-like evolution equations are derived, which are a generalization of the Whitham equations for fluid sloshing in three-dimensional rotating and translating coordinates. Moreover, the new variational principles are appended to Luke’s variational principle to present a unified variational framework for the hydrodynamic problem of interactions between gravity-driven potential-flow water waves and a freely floating rigid-body, dynamically coupled to its interior weakly dispersive nonlinear shallow-water sloshing in three dimensions.

Thermoelastic medium in the context of four theories subjected to gravity field and laser pulse

The paper aims at studying the impact of gravity and laser pulse on the overall structure of the generalized thermoelasticity equations concerning a standardized elastic isotropic half-space. Using four generalized thermoelasticity theories, i.e. the Green-Naghdi (GN) theory, Green-Lindsay (GL) theory, Lord-Schulman (LS) theory, and Coupled Theory (CT), the authors applied the formulation. In the physical sphere, they attained the analytical expressions for the (Mechanical and Maxwell’s) stresses distribution, displacement components, and temperature through utilizing the normal mode analysis. Moreover, they calculated these expressions numerically and plotted the conforming graphs to demonstrate and make comparisons between theoretical findings. The paper concludes that the impact of gravity and laser pulse field is highly significant.

Analytical study of two-dimensional thermo-mechanical responses of viscoelastic skin tissue with temperature-dependent thermal conductivity and rheological properties

The generalized thermo-viscoelastic theory without energy dissipation is used in this work to investigate the transfer of bioheat and the mechanical heat-induced response in a human skin plane tissue with variable thermal and rheological properties. Integral transformations are used for Laplace and Fourier. In the scheme of two-dimensional equations, the exponential matrix procedure, which forms the basis of the state-space approach of modern control theory, is applied. The resulting formulation is applied to a thermal shock half-space problem. The inversion process for Fourier and Laplace transforms is carried out using a numerical method based on Fourier series expansions. Comparisons between computational measurements and Penne’s experimental verification indicate that the Green–Naghdi (II) bioheat mathematical model is an effective method for estimating the transition of bioheat to viscoelastic skin tissue. The influences of variable thermal conductivity and volume materials properties on all fields are examined.

Thermomechanical Waves in an Axisymmetric Rotating Disk Using Refined Green–Naghdi Models

In this paper, four thermoelasticity models are applied to investigate the thermo-mechanical waves in an axisymmetric rotating disk. For this purpose, some modifications of Green and Naghdi’s generalized thermoelasticity theory have been made. These novel dual- and triple-phase-lag models are presented. The closed-form solution governing equations of thermomechanical waves in the rotating disk has been presented. Some validation results are tabulated to compare the simple and refined dual- and triple-phase lag models based upon the Green–Naghdi theory. The effects of dimensionless time and angular speed on all variables are investigated. The validity of results is acceptable and benchmark results are tabulated to aid other researchers in their upcoming comparisons.

Derivation of a Viscous Serre–Green–Naghdi Equation: An Impasse?

In this article, we present the current status of the derivation of a viscous Serre–Green–Naghdi system. For this goal, the flow domain is separated into two regions. The upper region is governed by inviscid Euler equations, while the bottom region (the so-called boundary layer) is described by Navier–Stokes equations. We consider a particular regime binding the Reynolds number and the shallowness parameter. The computations presented in this article are performed in the fully nonlinear regime. The boundary layer flow reduces to a Prandtl-like equation that we claim to be irreducible. Further approximations are necessary to obtain a tractable model.

Computational analysis of an infinite magneto-thermoelastic solid periodically dispersed with varying heat flow based on non-local Moore–Gibson–Thompson approach

In this investigation, a computational analysis is conducted to study a magneto-thermoelastic problem for an isotropic perfectly conducting half-space medium. The medium is subjected to a periodic heat flow in the presence of a continuous longitude magnetic field. Based on Moore–Gibson–Thompson equation, a new generalized model has been investigated to address the considered problem. The introduced model can be formulated by combining the Green–Naghdi Type III and Lord–Shulman models. Eringen’s non-local theory has also been applied to demonstrate the effect of thermoelastic materials which depends on small scale. Some special cases as well as previous thermoelasticity models are deduced from the presented approach. In the domain of the Laplace transform, the system of equations is expressed and the problem is solved using state space method. The converted physical expressions are numerically reversed by Zakian’s computational algorithm. The analysis indicates the significant influence on field variables of non-local modulus and magnetic field with larger values. Moreover, with the established literature, the numerical results are satisfactorily examined.

On High Order ADER Discontinuous Galerkin Schemes for First Order Hyperbolic Reformulations of Nonlinear Dispersive Systems

This paper is on arbitrary high order fully discrete one-step ADER discontinuous Galerkin schemes with subcell finite volume limiters applied to a new class of first order hyperbolic reformulations of nonlinear dispersive systems based on an extended Lagrangian approach introduced by Dhaouadi et al. (Stud Appl Math 207:1–20, 2018), Favrie and Gavrilyuk (Nonlinearity 30:2718–2736, 2017). We consider the hyperbolic reformulations of two different nonlinear dispersive systems, namely the Serre–Green–Naghdi model of dispersive water waves and the defocusing nonlinear Schrödinger equation. The first order hyperbolic reformulation of the Schrödinger equation is endowed with a curl involution constraint that needs to be properly accounted for in multiple space dimensions. We show that the original model proposed in Dhaouadi et al. (2018) is only weakly hyperbolic in the multi-dimensional case and that strong hyperbolicity can be restored at the aid of a novel thermodynamically compatible GLM curl cleaning approach that accounts for the curl involution constraint in the PDE system. We show one and two-dimensional numerical results applied to both systems and compare them with available exact, numerical and experimental reference solutions whenever possible.

Thermal diffusion of an unbounded solid with a spherical cavity via refined three-phase-lag Green–Naghdi models

This article deals with thermal diffusion vibration analysis in an unbounded medium including a spherical cavity. Multi single/dual-phase-lag models based upon the Green–Naghdi theory are obtained to discuss the thermoelastic diffusion of the spherical cavity. The surface of the cavity is traction and chemical potential free, not isolated, and subjected to a flux varying harmonically with time. A comparison of results is made, and the validity of results is acceptable. Benchmark outcomes are tabulated to aid other researchers in their future investigations.

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.

Discontinuous Galerkin methods for a dispersive wave hydro-sediment-morphodynamic model

A dispersive wave hydro-sediment-morphodynamic model developed by complementing the shallow water hydro-sediment-morphodynamic (SHSM) equations with the dispersive term from the Green–Naghdi equations is presented. A numerical solution algorithm for the model based on the second-order Strang operator splitting is presented. The model is partitioned into two parts, (1) the SHSM equations and (2) the dispersive correction part, which are discretized using discontinuous Galerkin finite element methods. This splitting technique provides a facility to select dynamically regions of a problem domain where the dispersive term is not applied, e.g. wave breaking regions where the dispersive wave model is no longer valid. Algorithms that can handle wetting–drying and detect wave breaking are provided and a number of numerical examples are presented to validate the developed numerical solution algorithm. The results of the simulations indicate that the model is capable of predicting sediment transport and bed morphodynamic processes correctly provided that the empirical models for the suspended and bed load transport are properly calibrated. Moreover, the developed model is able to accurately capture hydrodynamics and wave dispersion effects up to swash zones, and its application is justified for simulations where dispersive wave effects are prevalent.

Galerkin-type solution for the Moore–Gibson–Thompson thermoelasticity theory

It is prominent that the Galerkin-type representation plays a dominant role in probing various challenges of mathematical physics, continuum mechanics and occupies an important place in the field of partial differential equations (PDEs). Thus, the contemporary analysis of different boundary value problems (BVPs) in thermoelasticity theory commonly begins by analyzing the Galerkin-type representation of the field equations in terms of elementary functions (harmonic, biharmonic, and metaharmonic, etc). This work is aimed at formulating the representation of a Galerkin-type solution by means of elementary functions for the recently developed Moore–Gibson–Thompson (MGT) thermoelasticity theory. The MGT theory is a generalized form of the Lord–Shulman (LS) model as well as of the Green–Naghdi (GN) thermoelastic model. Here, we establish a theorem and derive the Galerkin-type solution for the basic governing equations under this theory. Later, the Galerkin representation of a system of equations for steady oscillations is derived. Based on this representation, we finally establish the general solution (GS) for the system of homogeneous equations of stable oscillation, neglecting the extrinsic body force and extrinsic heat supply.