Fictitious Models Research Articles

Analysis of singular perturbations on the Brinkman problem for fictitious domain models of viscous flows

We show the justification of a formulation by fictitious domain to study incompressible viscous flows inside fluid–porous–solid systems by using the Brinkman model in a heterogeneous fictitious porous medium covering the whole auxiliary domain. The singular perturbations of this problem are analysed when the permeability of the medium tends to infinity in the fluid domain and/or to zero in the solid domain. In addition, the viscosity inside the solid body may possibly tend to infinity. The strong convergence of the solutions is established. Some error estimates on the solution are derived as a function of the penalty parameter. The error bound on the resulting applied force for the flow around a bluff obstacle is also given. Copyright © 1999 John Wiley & Sons, Ltd.

Analysis of singular perturbations on the Brinkman problem for fictitious domain models of viscous flows

Analysis of singular perturbations on the Brinkman problem for fictitious domain models of viscous flows

Psychiatric contribution to the debate on films of the silent movie era in Germany

Literary writers and scientists of various disciplines have contributed to debates about the silent movie in the 10s and 20s in Germany, leading to basic insights into the structure and effects of the new film medium. Psychiatric authors of the documented period have elaborated propositions towards a theory of film perception and analyses of different possibly nocuous film effects. The hypothesis of a causal effect of the film medium on violence and the notion of a transmission of suicidal behaviour by fictitious film models are still controversially discussed.

On the use of SVD-improved point matching in the current-model method (EM scattering)

An approach which uses the singular value decomposition (SVD) to improve the accuracy of the numerical solution obtained with fictitious current models is introduced. In this approach, the SVD is essentially facilitating a systematic way to optimally reduce the generalized inverse matrix used in the solution to a submatrix of smaller rank. This reduction strikes a balance between the fulfillment of the boundary conditions at the matching points and that between them. Clearly, the boundary conditions errors at the matching points are no longer strictly zero. However, the previously discernible errors between the matching points are markedly suppressed. The approach is efficacious not only when the impedance matrix is inherently singular or highly ill conditioned, but also when this matrix is entirely well conditioned. It can be generalized and implemented in any method of moments code which uses point matching for testing. The approach has been incorporated into an existing solution based on the current-model method for the problem of scattering from periodic sinusoidal surfaces, and is shown to render the solution more accurate.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of scattering from structures containing a variety of length scales using a source-model technique

Fictitious source models have been applied extensively in recent years to a variety of electromagnetic and acoustic wave scattering problems. This paper is introducing an extension of the source-model technique that facilitates the solution to problems subsuming scatterers that contain a variety of length scales. This extension is in tune with the source-model technique philosophy of using simple sources the fields of which are analytically derivable. It amounts to letting the coordinates of some of the source centers assume complex values. Positioned in complex space, the simple sources radiate beam-type fields, which are more localized and are better approximations of the scattering from the smooth expanses of the structure. The coordinates of the other source centers retain their conventional real values. These latter sources are used, of course, to approximate the fields in the vicinity of the more rapidly varying expanses of the structure. The new approach is applied to analyze acoustic scattering from a structure comprising two adjacent pressure-release spheres of different size. It is found to render the solution computationally more effective at the expense of only a slight increase in its complexity.

Analysis of electromagnetic scattering using a current model method

Fictitious current models have been used extensively in recent years to facilitate a computational scheme for a variety of scattering problems. This paper reviews the basic philosophy behind this new approach and outlines the relevant formalism. A number of cases which shed light on various specialty aspects of the general technique are also described in some detail. The wide applicability and demonstrated success of the method are recorded.