21,294 research outputs found
Efficient solution of 3D electromagnetic eddy-current problems within the finite volume framework of OpenFOAM
Eddy-current problems occur in a wide range of industrial and metallurgical
applications where conducting material is processed inductively. Motivated by
realising coupled multi-physics simulations, we present a new method for the
solution of such problems in the finite volume framework of foam-extend, an
extended version of the very popular OpenFOAM software. The numerical procedure
involves a semi-coupled multi-mesh approach to solve Maxwell's equations for
non-magnetic materials by means of the Coulomb gauged magnetic vector potential
and the electric scalar potential. The concept is further extended on the basis
of the impressed and reduced magnetic vector potential and its usage in
accordance with Biot-Savart's law to achieve a very efficient overall modelling
even for complex three-dimensional geometries. Moreover, we present a special
discretisation scheme to account for possible discontinuities in the electrical
conductivity. To complement our numerical method, an extensive validation is
completing the paper, which provides insight into the behaviour and the
potential of our approach.Comment: 47 pages, improved figures, updated references, fixed typos, reverse
phase shift, consistent use of inner produc
Small object limit of Casimir effect and the sign of the Casimir force
We show a simple way of deriving the Casimir Polder interaction, present some
general arguments on the finiteness and sign of mutual Casimir interactions and
finally we derive a simple expression for Casimir radiation from small
accelerated objects.Comment: 13 pages, late
Efficient integral equation formulation for inductive waveguide components with posts touching the waveguide walls
In this paper a surface integral equation technique is employed for the analysis of inductive waveguide problems containing metallic or dielectric objects of arbitrary shape, focusing on the case where these objects are connected to the waveguide walls. Using the extinction theorem, the main problem is split into two problems. In the first one the parallel plate waveguide Green’s functions are used. Because of the choice of these functions, the side of the object touching the waveguide wall is not considered for discretization in a method of moments analysis. The second problem is applied inside the dielectric object, and uses the free space Green’s functions. It is shown that an additional spatial image is needed to impose the proper boundary conditions for the fields on the side touching the waveguide wall in the original problem. Results show the importance of including this additional image in the formulation for the correct behavior of the fields. With the proposed technique, the paper explores some alternatives for designing specific filter responses using dielectric posts inside cavity filters. Comparisons with a commercial finite elements tool demonstrate the accuracy of the proposed integral equation formulation.This work has been developed with support from the Spanish National Project (CICYT) with Ref TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with Ref 02972/PI/05
Conceptual design study for heat exhaust management in the ARC fusion pilot plant
The ARC pilot plant conceptual design study has been extended beyond its
initial scope [B. N. Sorbom et al., FED 100 (2015) 378] to explore options for
managing ~525 MW of fusion power generated in a compact, high field (B_0 = 9.2
T) tokamak that is approximately the size of JET (R_0 = 3.3 m). Taking
advantage of ARC's novel design - demountable high temperature superconductor
toroidal field (TF) magnets, poloidal magnetic field coils located inside the
TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket - this
follow-on study has identified innovative and potentially robust power exhaust
management solutions.Comment: Accepted by Fusion Engineering and Desig
Direct and Inverse Computational Methods for Electromagnetic Scattering in Biological Diagnostics
Scattering theory has had a major roll in twentieth century mathematical
physics. Mathematical modeling and algorithms of direct,- and inverse
electromagnetic scattering formulation due to biological tissues are
investigated. The algorithms are used for a model based illustration technique
within the microwave range. A number of methods is given to solve the inverse
electromagnetic scattering problem in which the nonlinear and ill-posed nature
of the problem are acknowledged.Comment: 61 pages, 5 figure
Geometry of the Casimir Effect
When the vacuum is partitioned by material boundaries with arbitrary shape,
one can define the zero-point energy and the free energy of the electromagnetic
waves in it: this can be done, independently of the nature of the boundaries,
in the limit that they become perfect conductors, provided their curvature is
finite. The first examples we consider are Casimir's original configuration of
parallel plates, and the experimental situation of a sphere in front of a
plate. For arbitrary geometries, we give an explicit expression for the
zero-point energy and the free energy in terms of an integral kernel acting on
the boundaries; it can be expanded in a convergent series interpreted as a
succession of an even number of scatterings of a wave. The quantum and thermal
fluctuations of vacuum then appear as a purely geometric property. The Casimir
effect thus defined exists only owing to the electromagnetic nature of the
field. It does not exist for thin foils with sharp folds, but Casimir forces
between solid wedges are finite. We work out various applications: low
temperature, high temperature where wrinkling constraints appear, stability of
a plane foil, transfer of energy from one side of a curved boundary to the
other, forces between distant conductors, special shapes (parallel plates,
sphere, cylinder, honeycomb).Comment: 44 pages, 8 figures; Proceedings of the 15 th SIGRAV Conference on
General Relativity and Gravitational Physics, Villa Mondragone, Monte Porzio
Catone, Roma, Italy, September 9-12, 200
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