A Node-based Smoothed Point Interpolation Method (NS-PIM) for Three-dimensional Thermoelastic Problems

A node-based smoothed point interpolation method (NS-PIM) is formulated to analyze 3-D steady-state thermoelastic problems subjected to complicated thermal and mechanical loads. Gradient smoothing technique with node-based smoothing domains is utilized to modify the gradient fields and to perform the numerical integration required in the weak form formulation. Numerical results show that NS-PIM can achieve more accurate solutions even when the 4-node tetrahedral mesh is used compared to the finite-element method (FEM) using the same mesh, especially for strains and hence stresses. Most importantly, it can produce an upper bound solution of the exact solution in energy norm for both temperature and stress fields when a reasonably fine mesh is used. Together with FEM, we now for the first time have a simple means to obtain both upper and lower bounds of the exact solution to complex thermoelastic problems.     

Tubular linear induction motor for hydraulic capsule pipeline. I.Finite element analysis

An axisymmetric model of the magnetic field of the tubular linear induction motor (TLIM) for application to hydraulic capsule pipelines is developed using finite element method (FEM) analysis. The FEM model is used to analyze a specific TLIM design at standstill for a given supply current. The finite element formulation of the field equations is discussed and the magnetic field contours at different instants of time are presented. FEM computation of the thrust compares very well with experimental data     

Numerical investigation on optimization of thermal analysis due to immersion of hybrid nanostructures in a fluid of shear dependent viscosity using the finite element method

This article considers the dispersion of hybrid and mono nanoparticles in a fluid with viscosity (Williamson) dependent on shear rate, over a heated surface moving with nonuniform velocity and exposed to a magnetic field in the presence of an applied current. Extensive modeling leads to complex coupled mathematical models that are solved numerically via the finite element method (FEM). Convergent simulations are run to investigate the role of parameters on the dynamics of flow fields. The magnetic field intensity plays a role in controlling the magnetohydrodynamic boundary layer thickness (BLT) and thermal radiation controls the thickness of thermal boundary layers (TBL). However, the magnetic field intensity is responsible for an increase in BLT. In contrast to this, thermal radiation plays a role in controlling the thickness of the TBL. The impact of shear rate dependent viscosity on velocity is remarkable for both fluids. The motion of both of the fluids slows down when viscosity varies as a function of shear rate. Viscosity depending on the shear rate has a significant impact on wall shear stress. It is observed from simulations that wall shear increases when the parameters appearing in the model for shear rate dependent viscosity are increased. However, this increase in wall shear stress associated with a hybrid nanofluid is greater than the increase in wall shear stress associated with a mono nanofluid.     

Finite Element Analysis of Thermal Buckling of Rectangular Laminated Composite Plates with Circular Cut-Out

In this work, thermal buckling analysis of symmetric and anti-symmetric laminated composite plates with a cut-out is presented. The plate is assumed to be subjected to a uniform temperature rise for different boundary conditions. The thermal buckling analysis is performed using the code developed in MATLAB software. The stiffness matrices and thermal force vector are derived according to first-order shear deformation theory (FSDT). To have more control on the mesh pattern around the cut-out, convenient meshes are manually constructed using a mesh generation algorithm in which mesh density around the hole can be controlled. The results of FEM code is compared with ABAQUS's solutions and with those available in the literature. After that, the effects of cut-out size, boundary conditions, plate aspect ratio, and stacking sequence on critical thermal buckling temperature are investigated for symmetric and anti-symmetric plates. Also, plates with cut-out located at positions other than the center of plate are investigated and useful conclusions are derived from the numerical results.     

Thermal Buckling Analysis of Perforated Functionally Graded Plates

In this research, the buckling behavior of functionally graded (FG) plates under thermal loading is investigated based on finite element analysis. It is assumed the plate is subjected to a uniform temperature rise across plate thickness. First-order shear deformation theory (FSDT) is utilized for developing the solution method. By using an appropriately designed mesh structure for a perforated plate, the critical thermal buckling temperature is obtained by numerical solution of the problem based on finite element method (FEM). The FG plate is perforated by multiple cutouts. The number of cutouts is assumed one, two, four, or six. Also different geometrical shapes of cutouts including triangle, square, rhombus, pentagon, hexagon, and circle are considered. The influence of the number of cutouts and their geometrical shapes on thermal buckling response is investigated. The effects of the number of sides of cutouts from three (triangle) to infinity (circle) are discussed. Two different boundary conditions are taken into account. Also the influences of the distance between the cutouts and the orientation of cutouts on critical buckling temperature are studied. In addition, the effects of the orientation of ellipse cutouts are studied. Some remarkable conclusions are gained that can be useful in practical applications.     

Tubular linear induction motor for hydraulic capsule pipeline. II.Finite element method (FEM) maximum thrust design

For part I see ibid., vol. 8, no.2, pp. 251-256 (1993). The axisymmetric analysis of the magnetic field and the finite element method (FEM) formulation of the tubular linear induction motor (TLIM) for application to hydraulic capsule pipelines was discussed in part I. In these studies a three-phase sinusoidal current source supplies the stationary windings to produce a traveling magnetic field inducing currents in the cylindrical capsule conducting wall to produce thrust on the capsule. The results of the different studies using the developed FEM tool show that by introducing iron elements in the pipe wall, the thrust can be increased. Five cases are discussed here, and the magnetic field contours for each case are presented. FEM computation of the thrust for all cases is compared to choose the design which produces the maximum thrust     

Global simulation of a silicon Czochralski furnace in an axial magnetic field

Control of melt flow in crystal growth process by application of the magnetic field is a practical technique for silicon single crystals. In order to understand the influence of axial magnetic field on the silicon melt flow and oxygen transport in a silicon Czochralski (Cz) furnace, a set of global numerical simulations was conducted using the finite-element method for the magnetic field strength from 0 to 0.3 T, the crystal rotation rates from 0 to 30 rpm and the crucible counter-rotation rates from 0 to −15 rpm. It was assumed that the flow was axisymmetric laminar in both the melt and the gas, the melt was incompressible and a constant temperature was imposed on the outer wall of the Cz furnace. The results indicate significantly different flow patterns, thermal and oxygen concentration fields in the melt pool when a uniform axial magnetic field is applied.     

Stresses in radiative annular fin under thermal loading and its inverse modeling using sine cosine algorithm (SCA)

This work presents a novel mathematical model for the analysis of thermal stresses in a radiative annular fin with temperature-dependent thermal conductivity and radiative parameter. An approximate analytical solution for thermal stresses is derived using a homotopy perturbation method (HPM)-based closed-form solution of steady-state nonlinear heat transfer equation, coupled with classical elasticity theory. The effect of thermal parameters on the temperature field and the thermal stress fields are discussed. The various thermal parameters, such as a parameter describing the temperature-dependent thermal conductivity, coefficient of thermal expansion, coefficient of radiative parameter, and the variable radiative parameter, are inversely estimated for a given stress field. For inverse modeling, a population-based sine cosine algorithm (SCA) was employed to estimate the thermal parameters. The inverse modeling is verified by using the estimated thermal parameters in the closed-form solution of stress field. The reconstructed stress fields obtained from the inversely estimated parameters are then compared with the reference stress field. Results show a very good agreement between the reference stress field and the inversely estimated stress fields.     

Thermoelastic study of a functionally graded annular fin with variable thermal parameters using semiexact solution

Abstract

In this paper, the thermoelastic behavior of a functionally graded material (FGM) annular fin is investigated. The material properties of the annular fin are assumed to vary radially. The heat transfer coefficient and internal heat generation are considered to be functions of temperature. A closed form solution of nonlinear heat transfer equation for the FGM fin is obtained using the homotopy perturbation method (HPM) which leads to nonuniform temperature distributions within the fin. The temperature field is then coupled with the classical theory of elasticity and the associated thermal stresses are derived analytically. For the correctness of the present closed form solution for the stress field, the results are compared with the ANSYS-based finite element method (FEM) solution. The present HPM-based closed form solution of the stress field exhibits a good agreement with the FEM results. The effect of various thermal parameters such as the thermogeometric parameter, conduction-radiation parameter, internal heat generation parameter, coefficient of variation of thermal conductivity, and the coefficient of thermal expansion on the thermal stresses are discussed. The results are presented in both nondimensional and dimensional form. The dimensional stress analysis discloses the suitability of FGM as the fin material in practical applications.     

Static characteristics of a new doubly salient permanent magnetmotor

In this paper, magnetic field analysis of a new doubly salient permanent magnet (DSPM) motor is carried out based on the finite element method (FEM). Hence, the corresponding static characteristics, including PM flux linkage, self-inductance, mutual inductance, and static torque are deduced (the interaction between the PM field and armature field are taken into account). New methods for measuring the motor inductance are also proposed. The theoretical analysis is verified by experimental results     

Conjugate heat transfer and thermal stress analysis of wire coil inserted tubes that are heated externally with uniform heat flux

Wire coil inserted tubes are important in engineering applications. The conjugate heat transfer and thermal stress, which is induced by temperature differences in the wire coil inserted tube sheet of heat transfer equipment, were studied numerically in the paper. Three different wire coil inserts, which have different pitches, are considered. The smooth tube is also considered for comparison. Uniform heat flux was applied from the external surface of the tube. Water has been used as fluid. The energy and governing flow equations were solved using a finite difference scheme. The finite element method (FEM) was used to compute the thermal stress fields. The effect of the different wire coils on the thermal stress has been discussed in terms of the results extracted from the FEM. It was found that the maximum thermal stresses ratio occurred in the case of p = 2d for 3 m/s mean water velocity. Some designs to reduce the thermal stress in the wire coiled tube sheet were suggested.     

Analysis of the Magnetic Effect on Entropy Generation in an Inclined Channel Partially Filled with a Porous Medium

The major objective of this work is to investigate the magnetic effect on heat-fluid and entropy generation interactions in a porous medium for a laminar, incompressible, non-Dracy model flow in an inclined channel. The flow field considered is composed of porous and clear viscous layers. The constant magnetic force is assumed to be acting parallel to the y-axis perpendicular to the walls. The governing equations related to flow and thermal fields, which are coupled and nonlinear, are solved for both clear fluid and porous regions by implementing the semi numerical-analytical techniques differential transform method (DTM) and generalized differential quadrature method (GDQM). While keeping the channel walls at different constant temperatures (isothermal walls), the influence of the applied magnetic field on velocity, temperature, and entropy generation are investigated and presented graphically with the corresponding physical interpretations. Additionally, the effect of dimensionless parameters such as the Hartmann number (Ha), formation factor (F), porous parameter (σ), Brinkman number (Br), and the angle of inclination (?) on velocity and temperature fields are examined. The entropy generation (N _s ) number for the physical system is derived and plotted using velocity and temperature profiles and dimensionless quantities. One of the main advantages of this study compared to similar studies is to give a straightforward open form solution by using DTM and GDQM. By applying these techniques it is possible to obtain a tractable and easily applicable recurative form of nonlinear field equations. In many similar studies it is said that the equations have been solved; however, neither solution procedure provides neither accuracy nor, even more important than these, clarity of applicability cases and limits of using the technique to the reader. In this work, these are presented in a simple way.     

Numerical simulation of thermal stress in tube-sheet of heat transfer equipment

The thermal stress induced by temperature difference in the tube-sheet of heat transfer equipment was studied in the paper. Finite element method (FEM) was used to compute the temperature and the stress fields. The effect of the tube-sheet thickness on the thermal stress has been discussed in terms of the results by FEM. Some measures to reduce or eliminate the thermal stress in the tube sheet are suggested. A new design of the structure of the flexible tube sheet was proposed.     

Magnetic field effects on natural convection around a horizontal circular cylinder inside a square enclosure filled with nanofluid

In this study, natural convection in a concentric annulus between a cold outer square and heated inner circular cylinders in presence of static radial magnetic field is investigated numerically using the lattice Boltzmann method. The inner and outer cylinders are maintained at constant uniform temperatures and it is assumed that all walls are insulating the magnetic field. The numerical investigation is carried out for different governing parameters namely; the Hartmann number, nanoparticles volume fraction and Rayleigh number. The effective thermal conductivity and viscosity of nanofluids are calculated using the Maxwell–Garnetts (MG) and Brinkman models, respectively. Also, the multi-distribution-function (MDF) model is used for simulating the effect of uniform magnetic field. The results reveal that the average Nusselt number is an increasing function of nanoparticle volume fraction as well as the Rayleigh number, while it is a decreasing function of the Hartmann number.     

Mixed convection flow in an inclined enclosure under magnetic field with thermal radiation and heat generation

The influence of thermal radiation and heat generation on an unsteady two-dimensional natural convection flow in an inclined enclosure heated from one side and cooled from the adjacent side under the influence of a magnetic field using staggered grid finite-difference technique has been studied. The governing equations have been solved numerically for streamlines, isotherms, local Nusselt numbers and the average Nusselt number for various values of thermal radiation and heat generation parameters by considering three different inclination angles and magnetic field directions, keeping the aspect ratio fixed. The results indicate that the flow pattern and temperature fields are significantly dependent on the above mentioned parameters. It is found that magnetic field suppresses the convection flow and its direction influences the flow pattern which results in the appearance of inner loop and multiple eddies.     

A FEM comparative analysis of the thermal efficiency among floors made up of clay,concrete and lightweight concrete hollow blocks

This paper presents a comparative non-linear thermal analysis for a total of eighteen different in situ cast floors varying both the constituent materials of the hollow blocks (clay, concrete and lightweight concrete) and the shape and number of recesses (six different block types) using the finite element method (FEM). Based on the non-linear thermal analysis of the different configurations by FEM and considering both upward and downward heat flows, it is possible to choose the best candidate floor from the thermal point of view. Mathematically, the non-linearity is due to the radiation boundary condition inside the recesses of the blocks. The comparative analysis of the floors is carried out from the finite element analysis through the two important parameters: the average mass overall thermal efficiency and the equivalent thermal conductivity. Finally, the results and conclusions reached in this work are exposed.     

Performance analysis of a brushless and exciterless AC generator

In this paper, the authors propose a novel form of brushless AC generator that does not require a shaft-mounted exciter. The constructional details and operating principle of the generator are described and a method for computing the steady-state performance, using a combined circuit and field approach, is introduced. The two-dimensional finite element method (FEM) is used for calculating the magnetic field distribution at different times-steps, from which the EMF and current waveforms can be accurately determined. A technique for optimizing the use of computer internal memory, with a view of improving the accuracy of solution, is briefly discussed. Computed and experimental performance of a 1 kVA prototype generator are presented     

Thermal fatigue on pistons induced by shaped high power laser. Part II: Design of spatial intensity distribution via numerical simulation

In the laser induced thermal fatigue simulation test on pistons, the high power laser was transformed from the incident Gaussian beam into a concentric multi-circular pattern with specific intensity ratio. The spatial intensity distribution of the shaped beam, which determines the temperature field in the piston, must be designed before a diffractive optical element (DOE) can be manufactured. In this paper, a reverse method based on finite element model (FEM) was proposed to design the intensity distribution in order to simulate the thermal loadings on pistons. Temperature fields were obtained by solving a transient three-dimensional heat conduction equation with convective boundary conditions at the surfaces of the piston workpiece. The numerical model then was validated by approaching the computational results to the experimental data. During the process, some important parameters including laser absorptivity, convective heat transfer coefficient, thermal conductivity and Biot number were also validated. Then, optimization procedure was processed to find favorable spatial intensity distribution for the shaped beam, with the aid of the validated FEM. The analysis shows that the reverse method incorporated with numerical simulation can reduce design cycle and design expense efficiently. This method can serve as a kind of virtual experimental vehicle as well, which makes the thermal fatigue simulation test more controllable and predictable.     

三维有限元网格的面切割自动生成方法

讨论了三维有限元网格被平面、三角形网、地形面切割时的各种情况,针对六面体单元和三棱柱单元的切割都提出了相应的算法,并用程序予以实现。这种切割方法可以细分有限元网格,生成复杂模型。通过实际例子验证了该法的可行性。     

An edge-based smoothed point interpolation method (ES-PIM) for heat transfer analysis of rapid manufacturing system

This paper formulates an edge-based smoothed point interpolation method (ES-PIM) for analyzing 2D and 3D transient heat transfer problems with mixed boundary conditions and complicated geometries. In the ES-PIM, shape functions are constructed using the polynomial PIM with the Delta function property for easy treatment of essential boundary conditions. A generalized smoothing technique is used to reconstruct the temperature gradient field within the edge-based smoothing domains. The generalized smoothed Galerkin weak form is then used to establish the discretized system equations. Our results show that the ES-PIM can provide more close-to-exact stiffness compared with the “overly-stiff” finite element method (FEM) and the “overly-soft” node-based smoothed point interpolation method (NS-PIM). Owing to this important property, the present ES-PIM provides more accurate solutions than standard FEM using the same mesh. As an example, a practical cooling system of the rapid direct plasma deposition dieless manufacturing is studied in detail using the present ES-PIM, and a set of “optional” processing parameters of fluid velocity and temperature are found.