GL Model on Reflection of P and SV Waves from the Free Surface of Thermoelastic Diffusion Solid Under Influence of the Electromagnetic Field and Initial Stress

This article is devoted to estimating the influence of magnetic field, electric field and initial stress in an elastic solid half-space under thermoelastic diffusion. The governing equations in the xz-plane are solved taking into consideration the Green–Lindsay (GL) model. The Reflection of dilatational (P) wave and Shear Vertical (SV) wave split into four waves: namely, P wave, thermal wave, mass diffusion wave and SV wave. The reflection phenomena of P and SV waves from the free surface of an elastic solid with thermoelastic diffusion under influence of magnetic field, electric field and initial stress is considered. The expressions for the reflection coefficients for the four reflected waves are obtained. These reflection coefficients are found to depend upon the angle of incidence θ of P and SV waves, thermoelastic diffusion, magnetic field, electric field and initial stress and other material parameters. The numerical values for the reflection coefficients are calculated analytically and presented graphically for varying values of these parameters.     

Dual Phase Lag Model on Magneto-Thermoelasticity Infinite Non-Homogeneous Solid Having a Spherical Cavity

In this article, the induced displacement, temperature and stress fields in an infinite non-homogeneous elastic medium with a spherical cavity are obtained in the context dual-phase-lag model. The surface of the cavity is stress free and is subjected to a thermal shock. The material is assumed to be elastic and has an inhomogeneity in the radial direction. The type of non-homogeneity is such that the elastic constants, thermal conductivity and density are proportional to the n ^th power of the radial distance. The solutions are obtained analytically employing the Laplace transforms technique. The numerical inversion of the transforms is carried out using Fourier series expansions. The stresses components, temperature and displacement are computed numerically and presented graphically. A comparison of the results is made for different theories. If the magnetic field is neglected, the results obtained are deduced as a special case from this study.     

A Plane Magnetothermoelastic Waves Reflection and Refraction Between Two Solid Media with External Heat Sources and Initial Stress

In this article, an estimation to illustrate the reflection and transmission of thermoelastic waves at the interface of two different thermoelastic solid half-spaces under initial stress, magnetic field, and external heat sources is made. The governing equations are considered for an isotropic and homogeneous generalized thermoelastic model under initial stress, heat sources, magnetic field, and perfect boundary condition. The reflected and transmitted waves amplitudes are obtained for the incidence of SV-waves. Approximate expressions are obtained as a special case from the present problem. The results obtained are computed numerically for the amplitude ratios under initial stresses and are displayed graphically. It appears that the effects of initial stress, magnetic field, and external heat sources are very pronounced on the propagation phenomena. If the magnetic field and heat sources are neglected, the results obtained then lead to the same results obtained by relevant authors.     

A Problem on Thermoelastic Interactions in an Infinite Medium with a Cylindrical Hole in Generalized Thermoelasticity III

The aim of the present article is to study the thermoelastic interactions in an infinite elastic medium with a cylindrical hole in the context of generalized thermoelasticity III, recently developed by Green and Nagdhi [1 A. E. Green and P. M. Nagdhi , On Undamped Heat Waves in an Elastic Solid , J. Thermal Stresses , vol. 15 , pp. 253 – 264 , 1992 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]]. The boundary of the hole is assumed to be stress free and is subjected to a ramp type heating. In order to make a comparison between this thermoelastic model with other thermoelastic models, the problem is formulated on the basis of three different theories of thermoelasticity, namely: the extended thermoelasticity proposed by Lord and Shulman [2 H. W. Lord and Y. Shulman , A Generalized Dynamical Theory of Thermoelasticity , J. Mech. Phys. Solids , vol. 15 , pp. 299 – 309 , 1967 .[Crossref], [Web of Science ®] , [Google Scholar]], the thermoelasticity without energy dissipation (Green and Nagdhi [3 A. E. Green and P. M. Nagdhi , Thermoelasticity Without Energy Dissipation , J. Elasticity , vol. 31 , pp. 189 – 209 , 1993 .[Crossref], [Web of Science ®] , [Google Scholar]]) and thermoelasticity with energy dissipation (thermoelasticity type III [1 A. E. Green and P. M. Nagdhi , On Undamped Heat Waves in an Elastic Solid , J. Thermal Stresses , vol. 15 , pp. 253 – 264 , 1992 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]]) in a unified way. The solutions for displacement, temperature and stresses are obtained with the help of Laplace transform procedure. Firstly the short time approximated solutions for three different theories have been obtained analytically. Then following a numerical method for the inversion of Laplace transforms, the numerical values of the physical quantities are also computed for the copper material and results are displayed in graphical forms to compare the results obtained from different models of generalized thermoelasticity.     

Effects of Three Phase Lags on Generalized Thermoelasticity for an Infinite Medium with a Cylindrical Cavity

The present work is concerned with the effects of three-phase lags on thermoelastic interactions due to step input in temperature on the stress free boundary of a cylindrical cavity in an unbounded medium. The problem is studied in the context of theory of generalized thermoelasticity with three phase lags (Roychoudhuri, [24 S. K. Roychoudhuri , On a Thermoelastic Three-Phase-Lag Model , J. Thermal Stresses , vol. 30 , pp. 231 – 238 , 2007 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]]) and the theory of thermoelasticity with energy dissipation (Green and Naghdi, [4 A. E. Green and P. M. Naghdi , On Undamped Heat Waves in an Elastic Solid , J. Thermal Stresses , vol. 15 , pp. 253 – 264 , 1992 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]]) in a unified way. Solution of the problem is obtained by using the Laplace transform technique. Significant dissimilarities between two models showing the effects of phase lags are pointed out on the basis of analytical as well as numerical results of the problem. A numerical method for the inversion of Laplace transform is employed.     

The Effect of Initial Stress on Thermoelastic Rotating Medium with Voids Due to Laser Pulse Heating with Energy Dissipation

This article reports studies on the rotation of initially stressed thermoelastic medium with voids subjected to thermal loading due to laser pulse. The bounding plane surface is heated by a non-Gaussian laser beam. The medium rotated with a uniform angular velocity. The problem was studied in the context of Green-Naghdi (G-N) theory of types II and III using the normal mode analysis method. The comparisons between the both types II and III of (G-N) theory in the presence and the absence of the rotation, the initial stress and for two values of time for considered medium are shown graphically.     

Thermoelastic Study of an Infinite Functionally Graded Body with a Cylindrical Cavity Using the Green-Naghdi Model

The thermoelastic problem of an infinite functionally graded body with a cylindrical cavity whose surface suffers time-dependent thermal shock in the context of type II and type III of Green-Naghdi theories is studied by using finite element method in time domain directly. The thermal and mechanical properties of functionally graded solid under consideration are assumed to vary as the power of the radial coordinate. The results, including temperature, stresses, and displacements are presented graphically and the results are also analyzed. The effects of functionally graded parameter and the damping coefficient (C _K ) in type III of Green–Naghdi theories are also studied.     

汽轮机旁路阀门阀体温度场和应力场分析

采用有限元分析方法时某330 MW电站机组的汽轮机旁路阀门进行模拟分析.在其备用工况和操作工况下,分析了阀门阀体的温度场和应力场,由此得出不同工况下温度场及其对应的应力场的变化规律,其中备用工况下阀门入口处阀体温度梯度最大,综合应力值也最大为68.8 MPa,操作工况下,阀体综合应力值随着开启时间的延续先降低后增长,随...     

汽机调节阀阀体三维瞬态温度场及应力场分析

提出阀门阀体有限元建模的有效方法,采用结构分析有限元方法,对国产125MW汽轮机主蒸汽调节阀阀体冷态,温态,热态启停工况的温度场,热应力场,机械应力场,综合应力场进行了分析计算,得出了关键点在冷态启停工况详细的温度场及其对应的热应力场的变化规律,并给出了阀体在机组温态,热态启停工况下的应力场的计算结果,估算了各态启动的阀体寿命损耗。     

On Reflection and Transmission of p- and Sv-Waves Phenomena at the Interface Between Solid-Liquid Media with Magnetic Field and Two Thermal Relaxation Times

In this research, we studied the reflection and transmission of thermoelastic wave at a solid-liquid interface under influence of two thermal relaxation times and magnetic field. The governing equations are introduced taking into consideration Green-Lindsay theory and Maxwell's stresses. After solving the governing equations, we found the two reflections and transmission coefficients of incident p-(primary) and SV- (Shear Vertical) waves in the presence of thermal relaxation times and a magnetic field. The boundary conditions at the interface have been applied. The appropriate expressions to find the amplitude ratios for the two incidence waves (p- and SV-waves) have been obtained. A numerical calculation is made for the reflection and transmitted coefficients of the incident waves, in which we study the effect of thermal relaxation times and magnetic field. The results obtained are presented graphically for the effect of magnetic field and relaxation times to display the phenomena physical meaning.     

Effect of magnetic field dependent viscosity and rotation on ferroconvection saturating a porous medium in the presence of dust particles

This paper deals with the theoretical investigation of the combined effect of magnetic field dependent (MFD) viscosity and rotation on ferroconvection saturating a porous medium in the presence of dust particles subjected to a transverse uniform magnetic field. For a flat fluid layer contained between two free boundaries, an exact solution is obtained. A linear stability analysis has been carried out to study the onset of ferroconvection. The cases of stationary convection and oscillatory modes have been discussed. In this paper, an attempt is also made to obtain the sufficient conditions for the non-existence of overstability.     

Analyses of Thermal Conduction and Stress Induced by Electric Current in an Infinite Thin Plate with an Elliptical Hole

Uniform electric current at infinity is applied to a thin infinite conductor with an elliptical hole disturbing the electric current, which gives rise to Joule heat, temperature increase and heat flux. Joule heat produces uniform and uneven temperature fields which in turn initiate thermal stress. These electrical current, Joule heat, temperature, heat flux and thermal stress analyses are carried out and their closed form solutions are obtained. The heat conduction problem is solved as a temperature boundary value problem. Figures of distribution of Joule heat, temperature, heat flux and stress are shown. A dislocation and a rotation terms for thermal stress analysis appear, which makes problem complex. Solutions of Joule heat, temperature, heat flux and thermal stress are nonlinear for the direction of electric current. For an infinite plate with a circular hole, stress components do not occur on the whole plate. As a special case, a crack problem is analyzed and intensities at the crack tip of each problem are investigated. Relations between melting temperature and electric current density, and between fracture toughness value and electric current density are investigated for some crack lengths for steel.     

基于FLAC及神经网络的初始地应力场反演

分别采用RBF网络和BP网络，利用FLAC进行正分析计算。依据测点的应力数据反演了计算区域的初始地应力场。结果表明，在样本数量相同的情况下，RBF神经网络反演分析的精度以及学习、收敛速度均优于采用BP网络的反演算法。     

某碾压混凝土重力坝温度场及应力场仿真研究

温度荷载是混凝土坝应考虑的主要荷载之一,而坝体会因温度应力过大从而导致产生温度裂缝,对大坝的安全运行产生不利影响。为避免在施工和运行过程中因温度应力超过坝体混凝土的容许应力而产生温度裂缝,基于热传导理论,针对某碾压混凝土重力坝施工期和运行期的整个过程,采用三维有限元数值仿真分析方法,进行了温度场和温度应力场的计算分析。计算结果表明：提出的温控施工方案可有效降低坝体的最高温度和温度应力,并且此施工方案可满足相关规范要求和该工程的温控设计要求。同时,此研究成果亦可为类似工程提供借鉴。     

Effect of rotation on plane waves of generalized electromagnetothermoelastics with diffusion for a half-space

This article is aimed at studying the effects of rotation on the model of generalized thermoelastic diffusion for a thermally, isotropic and electrically conducting half-space with rotation at the uniform angular velocity. The rotating half-space is initially placed in an external magnetic field with constant intensity and its bounding surface in contact with a permeating substance is taken to be traction free and subjected to a time-dependent thermal load and chemical potential. The system of Maxwell's equations is given and the generalized electromagnetothermoelastic diffusion coupled governing equations are established. The normal mode analysis is adopted to solve the problems and the exact expressions for the non-dimensional temperature, displacement, stress, induced magnetic field, induced electric field, chemical potential and concentration are gained and represented graphically. The effects of rotation are evaluated by comparing the results obtained in the presence and absence of rotation.     

Hall effects on the hydromagnetic free convective flow and mass transfer through a porous medium bounded by an infinite vertical porous plate with constant heat flux

Effects of Hall current on free convection and mass transfer flow through a porous medium bounded by a vertical surface when a uniform magnetic field acts in a plane which makes an angle x with the plane transverse to the plate have been analysed. An analytic solution of the problem is obtained and the effects of the Hall parameter and the permeability parameter, as well as the other parameters entering into the problem, are discussed and shown graphically.     

Numerical Study of the Effect of Imaginary Circle Diameter and Initial Flow Field on the Aerodynamic Field in a Tangentially Fired Furnace

INTRoDUCTIoNInthetangeatiallyfiringsystempulverized-coal-and-airjetsareinjectedintothefurnacethIoughslotbtirnersinfourcornersofthefUInace.Theaxesofburnersaretangellttooneorsevera1imaginarycir-clesinproperordertoformastablerotationalfireballwithhightemperatureinoperation.Sotheimag-inarydiameterofiisanimportantgeometricstructureparameterindesigningatangentiallyfiredfurnace,whichistheemphasisofthisstudy.Atpresent,theimaginarycirclediameterrkiisusuallydesignedwithsmallvalueandtheconcentricfir…     

Numerical Investigation of the Magnetic Field Effects on the Entropy Generation and Heat Transfer in a Nanofluid Filled Cavity with Natural Convection

This paper presents a numerical investigation of the entropy generation and heat transfer in a ferrofluid (water and 4% Fe₃O₄ nanoparticles) filled cavity with natural convection using a two phase mixture model and control volume technique. The effect of applying a nonuniform magnetic field on the entropy generation and heat transfer in the cavity and also the interaction of magnetic force and the buoyancy force are investigated. Based on the obtained results, applying a magnetic field will enhance the heat transfer mechanism. Furthermore, by applying the nonuniform magnetic field on the ferrofluid filled cavity with natural convection, the total entropy generation is decreased considerably at higher Rayleigh numbers. Therefore, applying a magnetic field can be considered as a suitable method for entropy generation minimization in order to have high efficiency in the system.     

Heat and mass transfer effects on MHD flow of a couple‐stress fluid in a horizontal wavy channel with viscous dissipation and porous medium

This paper looks at heat and mass transfer effects on an unsteady MHD flow of a couple‐stress fluid in a horizontal wavy porous space with travelling thermal waves in the presence of a heat source and viscous dissipation. Initially the temperatures of the walls are maintained at different constant temperatures. The analytical expressions for velocity, temperature, and concentration field are obtained by the regular perturbation technique. The results are presented graphically for various values of emerging dimensionless parameters of the problem and are discussed to show interesting aspects of the solution. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21040 PACS: 44.15.+a, 44.30.+f, 44.27.nd, 47.50.Cd     

Entropy generation minimization and nonlinear heat transport in MHD flow of a couple stress nanofluid through an inclined permeable channel with a porous medium,thermal radiation and slip

Irreversible losses and heat transport in a magnetohydrodynamic flow of a viscous, steady, incompressible, and fully developed couple stress Al₂O₃–water nanofluid through a sloping permeable wall channel with porous medium and under the effect of radiation heat flux and slip were analyzed. The fundamental equations were solved numerically by using Runge-Kutta together with the shooting technique and the results were in qualitative agreement with an exact solution obtained for a limit case. The impacts of couple stress, Darcy number, solid nanoparticle concentrations, conduction-radiation parameter, Hartmann number and hydrodynamic slip on flow, temperature, heat transport, and entropy production were examined. It was possible to achieve values of minimum entropy production not yet reported in previous studies. In this way, optimal values of couple stress and slip were obtained. The heat transport was also explored and optimal values of slip flow and conduction-radiation parameter with maximum heat transfer were found. Finally, in addition to the alumina, the distributions of velocity, temperature, and entropy generation in TiO₂–water and Cu–water were presented for different solid nanoparticle concentrations. It was obtained that the local entropy of TiO₂–water was lower than Cu–water and Al₂O₃–water in the channel bottom region while it was greater in the upper region.