Mathematical modelling and computer simulation of temperature distribution in inhomogeneous composite systems with imperfect interface

Many studies have been done previously on temperature distribution in inhomogeneous composite systems with perfect interface, having no discontinuities along it. In this paper we have determined steady state temperature distribution in two inhomogeneous composite systems with imperfect interface, having discontinuities in temperature and heat flux using decomposed immersed interface method and performed the numerical simulation on MATLAB

Wave reflection at a free interface in an anisotropic pyroelectric medium with nonclassical thermoelasticity

In this paper, the well-established two-dimensional mathematical model for linear pyroelectric materials is employed to investigate the reflection of waves at the boundary between a vacuum and an elastic, transversely isotropic, pyroelectric material. A comparative study between the solutions of (a) classical thermoelasticity, (b) Cattaneo–Lord–Shulman theory and (c) Green–Lindsay theory equations, characterised by none, one and two relaxation times, respectively, is presented. Suitable boundary conditions are considered in order to determine the reflection coefficients when incident elasto–electro–thermal waves impinge the free interface. It is established that, in the quasi-electrostatic approximation, three different classes of waves: (1) two principally elastic waves, namely a quasi-longitudinal Primary (qP) wave and a quasi-transverse Secondary (qS) wave; and (2) a mainly thermal (qT) wave. The observed electrical effects are, on the other hand, a direct consequence of mechanical and thermal phenomena due to pyroelectric coupling. The computed reflection coefficients of plane qP waves are found to depend upon the angle of incidence, the elastic, electric and thermal parameters of the medium, as well as the thermal relaxation times. The special cases of normal and grazing incidence are also derived and discussed. Finally, the reflection coefficients are computed for cadmium selenide observing the influence of (1) the anisotropy of the material, (2) the electrical potential and (3) temperature variations and (4) the thermal relaxation times on the reflection coefficients

A High Order Solution of Three Dimensional TIME Dependent Nonlinear Convective-diffusive Problem Using Modified Variational Iteration Method

In this paper, we have achieved high order solution of a three dimensional nonlinear diffusive-convective problem using modified variational iteration method. The efficiency of this approach has been shown by solving two examples. All computational work has been performed in MATHEMATICA

Discrete Simulation of Gas-solid Flow and Softening-melting Behaviour in a Blast Furnace

The blast furnace is a complicated multiphase flow reactor with hazardous working conditions, and its understanding is still a challenge in research community. In the recent decades, the discrete element modelling is becoming a popular tool to study this process, especially for the particle related phenomena, such as gas-solid flow, particle softening-melting behaviour and gas-solid heat transfer. This work aims to develop some new and better methods to describe this process based on the discrete model. The discrete model shows some unique advantages in describing particle motion; however the high computing cost limits its application in the study of blast furnace. A sector model is successfully developed to represent the full 3D cylinder vessel, which can effectively reduce the number of particles and hence the computational cost. Its validity is first examined through two common industrial processes; hopper flow and pile formation. The results generated by the sector model are exactly the same as the full 3D model, but saved 90% computing time. Then, the sector model is applied to study the gas-solid flow in a blast furnace, and the comparison between the sector model and the slot model are given in detail. Understanding the particle softening and melting behavior in the cohesive zone is the basis to describe the gas/liquid distribution and thermal-chemical behavior in this zone, which is critical to understanding the complex physical and chemical phenomena in a blast furnace. The CFD-DEM method accompanying with the gas-particle heat transfer is one powerful tool to carry out this study. The softening and melting behaviour of wax particles is successfully captured, by implementing the correlation between Young’s modulus and temperature of wax. And the multi-layer behaviour is also studied and then a parametric study. Further, in order to study the heat transfer in the raceway of blast furnace, the gas-solid heat transfer based on the discrete model is first used in a moving bed. The simulation is quantitatively consistent with the previous experimental data, that demonstrating the capability to accurately describe the thermal phenomenon in the raceway

Virgin Passive Colon Biomechanics and a Literature Review of Active Contraction Constitutive Models

The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine

A New Boundary Element Technique For One- And Two-Temperature Models Of Biothermomechanical Behavior Of Anisotropic Biological Tissues

The main objective of this paper is to develop a novel boundary element technique for describing the three-dimensional (3D) biothermomechanical behavior of anisotropic biological tissues. The governing equations are studied on the basis of the dual phase lag bioheat transfer and Biot's theory for oneand two-temperature models. Because of the benefits of CQBEM, such as not being restricted by the complex shape of biological tissues and not requiring discretization of the interior of the treated region, it can cope with complex bioheat models and has low use of RAM and CPU. CQBEM is therefore a flexible and efficient tool for modeling the distribution of bioheat in anisotropic biological tissues and associated deformation. The resulting linear equations arising from CQBEM are solved by the generalized modified shift-splitting (GMSS) iterative method which reduces the number of iterations and the total time of the CPU. Numerical findings show the validity, efficacy and consistency of the proposed technique

A numerical simulation of the full two-dimensional electrothermal de-icer pad

The ability to predict the time-temperature history of electrothermal de-icer pads is important in the subsequent design of improved and more efficient versions. These de-icer pads are installed near the surface of aircraft components, for the specific purpose of removing accreted ice. The proposed numerical model can incorporate the full 2-D geometry through a section of a region (i.e., section of an airfoil), that current 1-D numerical codes are unable to do. Thus, the effects of irregular layers, curvature, etc., can now be accounted for in the thermal transients. Each layer in the actual geometry is mapped via a body-fitted coordinate transformation into uniform, rectangular computational grids. The relevant heat transfer equations are transformed and discretized. To model the phase change that might occur in any accreted ice, in an enthalpy formulation the phase change equations are likewise transformed and discretized. The code developed was tested against numerous classical numerical solutions, as well as against experimental de-icing data on a UH1H rotor blade obtained from the NASA Lewis Research Center. The excellent comparisons obtained show that this code can be a useful tool in predicting the performance of current de-icer models, as well as in the designing of future models

Modeling and simulation in tribology across scales: An overview

This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions