19.04.2012 to 21.04.2012

Kunle Olukotun

Stanford University

Kunle Olukotun

20.04.2012

Horacio Gonzalez-Velez

Robert Gordon University

Horacio Gonzalez-Velez

20.04.2012

Matthias Christen

Universita della Svissera Italiana

Matthias Christen

22.03.2012

Nick Trefethen

University of Oxford

Nick Trefethen

‘JACOBI 1825, CAUCHY 1826, POISSON 1827’

This visit was joint with ACM Seminar Series

01.03.2012

Konstatinos Zygalakis

University of Southampton & EPFL

Konstatinos Zygalakis

Qualitative Behaviour of Numerical Methods for SDEs and Applications

22.02.2012 to 24.02.2012

Gabriel Stoltz

CERMICS, Ecolde des Ponts ParisTech

Gabriel Stoltz

19.01.2012

Patrick Lam

University of Waterloo, Canada

Patrick Lam

‘Views, Programming Languages Research, and HPC’

09.01.2012 to 10.01.2012

Michael Giles

University of Oxford

Michael Giles

29.11.2011

Jean-Francois Remacle

Université catholique de Louvain

Title: Generation of probably correct curvilinear meshes

Abstract:  There is a growing consensus that state of the art Finite Volume technology requires, and will continue to require too extensive computational resources to provide the necessary resolution, even at the rate that computational power increases. The requirement for high resolution naturally leads us to consider methods which have a higher order of grid convergence than the classical (formal) 2nd order provided by most industrial grade codes. This indicates that higher-order discretization methods will replace at some point the finite volume solvers of today, at least for part of their applications.

The development of high-order numerical technologies for CFD is underway for many years now.

For example, Discontinuous Galerkin methods (DGM) have been largely studied in the literature, initially in a quite theoretical context, and now in the application point of view. In many contributions, it is shown that the accuracy of the method strongly depends of the accuracy of the geometrical discretization. In other words, the following question is raised: it is true that we have the high order methods, but how do we get the meshes?

08.11.2011

Timo Betcke

University College London

Title : Spectral decompositions and non-normality of boundary integral operators in acoustic scattering.

Abstract: Spectral properties of boundary integral operators in acoustic scattering are essential to understand properties such as coercivity or convergence of iterative methods. Yet, very little is known apart from the unit disk case, where the Green's function has a simple decomposition into Fourier modes. For more general domains it is not even known whether boundary integral operators are normal. In this talk we first extend known results about eigenvalues on the circle to the case of an ellipse, where a decomposition of the acoustic Green's function in elliptic coordinates is possible. Based on this it is shown that scaled versions of the standard boundary integral operators are normal in a modified $L^2$ inner product on the ellipse. For more general domains we will define approximate decompositions with fast decaying errors, that are normal in a scaled L^2 inner product and thereby demonstrate that boundary integral operators are in some sense close to normal operators also on general domains. We will present numerical examples on several interesting domains that show how non-normality influences the properties and the numerical behavior of boundary integral operators.

 

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