Diffusion in Solids and Liquids II, DSL-2006 II

Paper Title Page

Authors: Isaac Arellano, Gabriel Plascencia, Elías Carrillo, Miguel A. Barrón, Adolfo Sánchez, Juliana Gutiérrez
Abstract: In this paper we propose the design of a novel induction furnace for glass melting. The design is based on a mathematical analysis and performed numerically by means of the Finite Element Method. Several induction coils configurations were tested. The results from the mathematical model show that it is possible to melt glass in a furnace whose hearth is no larger than half a metre by using axial induction coils and high frequencies. This furnace configuration may result in increased glass melting rates along with the elimination of harmful emissions.
Authors: Gabriel Plascencia, Torstein A. Utigard, Juliana Gutiérrez, David Jaramillo, Vicente Mayagoitia, Marcello L. Hernández-Pichardo
Abstract: A three dimensional numerical heat transfer model has been developed to estimate the heat flux trough furnace side walls protected with water cooled cooling fingers. The model was set up by means of the finite element method. Materials with different thermal conductivity were modelled and the results obtained with the mathematical model were compared with experimental data. In every case, it was found excellent agreement between the experimental data and the model computations.
Authors: Marina Dubatovskaya, Sergei Rogosin
Abstract: We consider steady potential heat conduction of a cylindrical composite material with the special geometry. The matrix is modelling by the unit disc with di®erent conductivity of six equal sectors. Inclusions (having di®erent conductivity too) are symmetrically situated discs non-intersecting boundary of sectors. Mixed boundary conditions on parts of the boundary of matrix and matrix-inclusions leads to di®erent model of composite materials. A new method to study the corresponding mathematical model is proposed. It is based on the reduction of the problem to the vector-matrix boundary value problem for analytic vectors. The method is connected with the approach by Zhorovina and Mityushev to the study of R-linear boundary value on a fan-shaped domain.
Authors: Sergei Rogosin, Tatsyana Vaitekhovich
Abstract: Melting/freezing process with two dendrits (or freeze “pipes”) is modelled by the complex Hele-Shaw moving boundary value problem in a doubly connected domain. The later is equivalently reduced to a couple of problems, namely, to the linear Riemann-Hilbert boundary value problem in a doubly connected domain and to evolution problem, which can be written in a form of an abstract Cauchy-Kovalevsky problem. The later is studied on the base of Nirenberg-Nishida theorem, and for the former a generalization of the Schwarz Alternation Method is proposed. By using composition of these two approaches we get the local in time solvability of this couple of problems in appropriate Banach space setting.
Authors: César A.C. Sequeira
Abstract: In the history of electrode processes, intermediates are of extraordinary interest. In the lecture which follows, the most common types of intermediates in electrode processes are classified. Secondly, most of the methods which are available and have been used in finding intermediates are characterised. Thirdly, the principles of detection of intermediate and final products of electrode processes on the basis of kinetic information obtained by means of the rotating ring-disc electrode method are discussed. This approach is used for identification of the products of an organic electroreduction. In conclusion, it is demonstrated that the cathodic reduction of such organic compounds involves formation of stable and unstable intermediates.
Authors: M. Ghazinejad, Ali Shokuhfar
Abstract: In this paper the effect of stress induced phase transformation on the vibration response of SMA structures has been studied. To this end, a Ni-Ti clamped-free rod in the superelastic range which is subjected to axial harmonic loading has been considered. Subsequently, the dynamic behavior of the superelastic rod has been analyzed using Auricchio’s superelastic model, which can reproduce the superelastic behavior of the sample during stress induced phase transformation, and Finite Element Method. Obtained Results show that due to the phase transformation the dynamic behavior of superelastic rod is highly nonlinear. Also, it can be deduced that superelastic components with large hysteresis loop has the potential for use in vibration attenuation of structures.
Authors: Antonio C.M. Sousa, Fangming Jiang
Abstract: Heat and mass transfer and fluid flow in porous media are usually characterized by, or associated with, the effective thermal conductivity, the effective mass diffusivity and the permeability, respectively. All these macroscopic quantities are conceptually established on a phenomenological “equivalence” basis. They may contain the influence of porous micro-structures upon the corresponding diffusive process; however, the detailed nature inside the porous medium is lumped and neglected. Pore scale numerical modelling has the potential of providing adequate meso-/micro- scale insight into the transport process in porous medium, as well as obtaining macroscopic properties, which can encompass the complex pore-structure details. Modelling heat/mass transfer and fluid flow in complicated porous micro-structures presents a major challenge to numerical methods due to their multiscale and multiphysics nature. A relatively-novel numerical technique - the meshless Lagrangian-based Smoothed Particle Hydrodynamics (SPH) method is thought to be capable of making a significant contribution to this research field. This work deals primarily with the SPH modelling of heat conduction and fluid flow in 2-D isotropic porous media. The porous matrix is formed by randomly including a different component into a base component. Various pore-structures are realized by changing the inclusion shape/size, or the relative arrangement condition between inclusions. Pore-scale heat transfer and fluid flow streams are visualized, and both heat transfer and fluid flow always follow, as expected, the paths of least resistance through the porous structures. In what concerns the effective thermal conductivity, for the porous media with the base component of larger bulk thermal conductivity, the “flexible” EMT model, which can accommodate, to some extent, the influence from the porous micro-structures on the effective thermal conductivity by adjusting the so-called flexible factor ff, gives effective thermal conductivities agreeable to the SPH predictions across the whole composition range if ff is taken to be ~ 4.5; the effective thermal conductivity shows a weak dependence on the inclusion shape/size and the relative arrangement condition between inclusions; however, for porous media with dispersed inclusions, which component has larger bulk thermal conductivity presents a strong effect upon the effective thermal conductivity. The SPH fluid flow simulation results confirm the macroscopic Darcy’s law to be valid only in the creeping flow regime; the dimensionless permeability (normalized by the squared characteristic dimension of the inclusions) is found to have an exponential dependence on the porosity within the intermediate porosity range, and the derived dimensionless permeability /""porosity relation is found to have only a minor dependence on either the relative arrangement condition between inclusions or the inclusion shape/area.
Authors: Matej Vesenjak, Andreas Öchsner, Zoran Ren
Abstract: In this paper the behavior of hexagonal honeycombs under dynamic in-plane loading is described. Additionally, the presence and influence of the filler gas inside the honeycomb cells is considered. Such structures are subjected to very large deformation during an impact, where the filler gas might strongly affect their behavior and the capability of deformational energy absorption, especially at very low relative densities. The purpose of this research was therefore to evaluate the influence of filler gas on the macroscopic cellular structure behavior under dynamic uniaxial loading conditions by means of computational simulations. The LS-DYNA code has been used for this purpose, where a fully coupled interaction between the honeycomb structure and the filler gas was simulated. Different relative densities, initial pore pressures and strain rates have been considered. The computational results clearly show the influence of the filler gas on the macroscopic behavior of analyzed honeycomb structures. Because of very large deformation of the cellular structure, the gas inside the cells is also enormously compressed which results in very high gas temperatures and contributes to increased crash energy absorption capability. The evaluated results are valuable for further research considering also the heat transfer in honeycomb structures and for investigations of variation of the base material mechanical properties due to increased gas temperatures under impact loading conditions.
Authors: Matej Vesenjak, Andreas Öchsner, Zoran Ren
Abstract: The study describes the behavior of regular closed-cell cellular structure with gaseous fillers under impact conditions and consequent post-impact thermal conduction due to the compression of filler gas. Two dependent but different analyses types have been carried out for this purpose: (i) a strongly coupled fluid-structure interaction and (ii) a weakly coupled thermalstructural analysis. This paper describes the structural analyses of the closed-cell cellular structure under impact loading. The explicit code LS-DYNA was used to computationally determine the behavior of cellular structure under compressive dynamic loading, where one unit volume element of the cellular structure has been discretised with finite elements considering a simultaneous strongly coupled interaction with the gaseous pore filler. Closed-cell cellular structures with different relative densities and initial pore pressures have been considered. Computational simulations have shown that the gaseous filler influences the mechanical behavior of cellular structure regarding the loading type, relative density and type of the base material. It was determined that the filler’s temperature significantly increases due to the compressive impact loading, which might influence the macroscopic behavior of the cellular structure.
Authors: Matej Vesenjak, Zoran Žunič, Andreas Öchsner, Zoran Ren
Abstract: The paper describes the post-impact thermal conduction of regular closed-cell cellular structure with gaseous fillers due to the dynamic compression. Two different but subsequent computational analyses have been carried out for this purpose. To define the behavior of the cellular structure under compressive dynamic loading, a unit volume element of the cellular structure has been analyzed with the explicit finite element code LS-DYNA by considering a strongly coupled interaction of the cellular structure base material with the gaseous pore filler. The resulting deformed cellular structure has then been imported in the finite volume code ANSYS CFX 10.0 for further weakly coupled thermal-structural analyses of post-impact heat conduction through the base material and filler gas. The increased temperature and pressure of the filler gas after compressive impact loading from the initial analyses have been used as initial conditions for the thermal analyses, where only the heat conduction due to the gas compression has been taken into account. This paper considers only the closed-cell cellular structure with two different relative densities and air inside the pores. Computational simulations have shown a low overall temperature increase of the cellular structure due to filler gas compression. The temperature increase of the base material is expected to be higher at lower relative densities. The presented procedure illustrates a convenient approach to solving strongly coupled fluid-structure interaction problems by considering also a weakly coupled thermal-structural solution, which can be used for a wide range of engineering applications.

Showing 21 to 30 of 39 Paper Titles