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Coupling Term (coupling + term)

Distribution by Scientific Domains

Physics and Astronomy	37%
Chemistry	25%

Selected Abstracts

On the L2 and the H1 couplings for an overlapping domain decomposition method using Lagrange multipliers

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2007
P.-A. Guidault
Abstract In this paper, a comparison of the L2 and the H1 couplings is made for an overlapping domain decomposition method using Lagrange multipliers. The analysis of the local equations arising from the formulation of the coupling of two mechanical models shows that continuous weight functions are required for the L2 coupling term whereas both discontinuous and continuous weight functions can be used for the H1 coupling. The choice of the Lagrange multiplier space is discussed and numerically studied. The paper ends with some numerical examples of an end-loaded cantilever beam and a cracked plate under tension and shear. It is shown that the continuity enforced with the H1 coupling leads to a link with a flexibility that can be beneficial for coupling a very coarse mesh with a very fine one. To limit the effect of the volume coupling on the global response, a narrow coupling zone is recommended. In this case, volume coupling tends to a surface coupling, especially with a L2 coupling. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A coupled DEM/CFD analysis of the effect of air on powder flow during die filling

AICHE JOURNAL, Issue 1 2009
Y. Guo
Abstract Die filling from a stationary shoe in a vacuum and in the presence of air was numerically analyzed using an Eulerian-Lagrangian model, which employs a discrete element method (DEM) for the particles and computational fluid dynamics (CFD) for the air with a two-way air-particle interaction coupling term. Monodisperse and polydisperse powder systems have been simulated to explore the effect of the presence of air on the die filling process. For die filling with monodisperse powders, the influences of particle size and density on the flow behavior were explored. The numerical simulations revealed that the presence of air has a significant impact on the powder flow behavior, especially for systems with smaller and/or lighter particles. Flow has been characterized in terms of a dimensionless mass flow rate, and it has been shown that for die filling in a vacuum this is constant. The flow characteristics for die filling in air can be classified into two regimes. There is an air-inert regime in which the particle size and density are sufficiently large that the effect of air flow becomes negligible, and the dimensionless mass flow rate is essentially identical to that obtained for die filling in a vacuum. There is also an air-sensitive regime, for smaller particle sizes and lower particle densities, in which the dimensionless mass flow rate increases as the particle size and density increase. The effects of particle-size distribution and adhesion on the flow behavior have also been investigated. It was found that, in a vacuum, the dimensionless mass flow rate for polydisperse systems is nearly identical to that for monodisperse systems. In the presence of air, a lower dimensionless mass flow rate is obtained for polydisperse systems compared to monodisperse systems, demonstrating that air effects become more significant. Furthermore, it has been shown that, as expected, the dimensionless mass flow rate decreases as the surface energy increases (i.e., for more cohesive powders). © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Approximate analytical solutions of the pseudospin symmetric Dirac equation for exponential-type potentials

ANNALEN DER PHYSIK, Issue 10-11 2009
A. Arda
Abstract The solvability of The Dirac equation is studied for the exponential-type potentials with the pseudospin symmetry by using the parametric generalization of the Nikiforov,Uvarov method. The energy eigenvalue equation, and the corresponding Dirac spinors for Morse, Hulthen, and q -deformed Rosen,Morse potentials are obtained within the framework of an approximation to the spin-orbit coupling term, so the solutions are given for any value of the spin-orbit quantum number , = 0, or , , 0. [source]

Approximate analytical solutions of the pseudospin symmetric Dirac equation for exponential-type potentials

Bridging domain methods for coupled atomistic,continuum models with L2 or H1 couplings

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2009
P.-A. Guidault
Abstract A bridging domain method for coupled atomistic,continuum models is proposed that enables to compare various coupling terms. The approach does not require the finite element mesh to match the lattice spacing of the atomic model. It is based on an overlapping domain decomposition method that makes use of Lagrange multipliers and weight functions in the coupling zone in order to distribute the energy between the two competing models. Two couplings are investigated. The L2 coupling enforces the continuity of displacements between the two models directly. The H1 coupling involves the definition of a strain measure. For this purpose, a moving least-square interpolant of the atomic displacement is defined. The choice of the weight functions is studied. Patch tests and a graphene sheet with a crack are studied. It is shown that both continuous and discontinuous weight functions can be used with the H1 coupling whereas the L2 coupling requires continuous weight functions. For the examples developed herein, the L2 coupling produces less error in the zone of interest. The flexibility of the H1 coupling with constant weight function may be beneficial but the results may be affected depending on the topology of the bridging zone. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Locking-free finite elements for shear deformable orthotropic thin-walled beams

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2007
F. Minghini
Abstract Numerical models for finite element analyses of assemblages of thin-walled open-section profiles are presented. The assumed kinematical model is based on Timoshenko,Reissner theory so as to take shear strain effects of non-uniform bending and torsion into account. Hence, strain elastic-energy coupling terms arise between bending in the two principal planes and between bending and torsion. The adopted model holds for both isotropic and orthotropic beams. Several displacement interpolation fields are compared with the available numerical examples. In particular, some shape functions are obtained from ,modified' Hermitian polynomials that produce a locking-free Timoshenko beam element. Analogously, numerical interpolation for torsional rotation and cross-section warping are proposed resorting to one Hermitian and six Lagrangian formulation. Analyses of beams with mono-symmetric and non-symmetric cross-sections are performed to verify convergence rate and accuracy of the proposed formulations, especially in the presence of coupling terms due to shear deformations, pointing out the decay length of end effects. Profiles made of both isotropic and fibre-reinforced plastic materials are considered. The presented beam models are compared with results given by plate-shell models. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Quantization of the ab initio nonadiabatic coupling matrix: The C2H molecule as a case study

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2001
Michael Baer
Abstract The observation that, for a given sub-Hilbert space, diabatic potentials, just like adiabatic potentials, have to be single-valued in configuration space led to the unavoidable conclusion that the relevant nonadiabatic coupling matrix (i.e., the matrix that contains the vectorial electronic nonadiabatic coupling terms) has to be quantized along any contour in configuration space. In the present article this statement is tested with respect to the three (excited) states of the C2H molecule, i.e., the 22A,, 32A,, and 42A, states. For this purpose ab initio electronic nonadiabatic coupling matrices were calculated along various contours surrounding the relevant conical intersections (one conical intersection between the 22A, and 32A, states and two conical intersections between the 32A, and 42A, states). Employing the line-integral technique it was shown that as long as the contour that surrounds the (2,3) conical intersection is close enough to the CI and avoids the two (3,4) conical intersections, the 2×2 nonadiabatic coupling matrices are quantized. However they fail to be quantized for contours that also surround one or two of the other conical intersections. In this case one is obliged to employ the three-state nonadiabatic coupling matrix. Doing that, it was shown that it is the 3×3 matrices that satisfy the quantization condition. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 [source]

A self-consistent treatment of the electromotive force in magnetohydrodynamics for large diffusivities

ASTRONOMISCHE NACHRICHTEN, Issue 7 2010
A. Courvoisier
Abstract The coupled equations that describe the effect of large-scale magnetic and velocity fields on forced high-diffusivity magnetohydrodynamic flows are investigated through an extension of mean field electrodynamics. Our results generalise those of Rädler & Brandenburg (2010), who consider a similar situation but assume that the effect of the Lorentz force on the momentum equation can be neglected. New mean coupling terms are shown to appear, which can lead to large-scale growth of magnetic and velocity fields even when the usual a-effects are absent (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]