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Mittwoch, 19.12.2018, 11:30 Uhr (WIAS-406)
Seminar Interacting Random Systems
C. Betken, Universität Osnabrück:
Dynamic random graphs: Sedentary random waypoint and preferential attachment models
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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Seminar Interacting Random Systems

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WIAS Berlin
Donnerstag, 10.01.2019, 14:00 Uhr (WIAS-ESH)
Seminar Numerische Mathematik
Dr. N. Ahmed, Lahore University of Management Sciences, Pakistan:
Numerical comparisons of finite element stabilized methods for a 2D vortex dynamics simulation at high Reynolds number
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
In this talk, I will present an up-to-date and classical Finite Element (FE) stabiliz ed methods for time-dependent incompressible flows. All studied methods belong to the Variational MultiScale (VMS) framework. So, different realizations of stabilized FE-VMS methods are compared in a high Reynolds number vortex dynamics simulation. In particular, a fully Residual-Based (RB)-VMS method is compared with the classical Streamline-Upwind Petrov--Galerkin (SUPG) method together with grad-div stabilization, a standard one-level Local Projection Stabilization (LPS) method, and a recently proposed LPS method by interpolation. These procedures do not make use of the statistical theory of equilibrium turbulence, and no ad-hoc eddy viscosity modeling is required for all methods. Applications to the simulation of a high Reynolds numbers flow with vortical structures on relatively coarse grids are showcased, by focusing on a two-dimensional plane mixing-layer flow. Both Inf-Sup Stable (ISS) and Equal Order (EO) (H^1)-conforming FE pairs are explored, using a second-order semi-implicit Backward Differentiation Formula (BDF2) in time. Based on the numerical studies, it is concluded that the SUPG method using EO FE pairs performs best among all methods. Furthermore, there seems to be no reason to extend the SUPG method by the higher order terms of the RB-VMS method.

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WIAS Berlin
Mittwoch, 23.01.2019, 11:30 Uhr (WIAS-406)
Seminar Interacting Random Systems
P. Houdebert, Aix-Marseille Université, Frankreich:
Sharp phase transition for the Widom-Rowlinson model
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstrakt
The Widom-Rowlinson model is formally defined as two homogeneous Poisson point processes forbidding the points of different type to be too close. For this Gibbs model the question of uniqueness/ non-uniqueness depending on the two intensities is relevant. This model is famous because it was the first continuum Gibbs model for which phase transition was proven, in the symmetric case of equal intensities large enough. But nothing was known in the non-symmetric case, where it is conjectured that uniqueness would hold. In a recent work with D. Dereudre (Lille), we partially solved this conjecture, proving that for large enough activities the phase transition is only possible in the symmetric case of equal intensities. The proof uses percolation and stochastic domination arguments.

Weitere Informationen
Seminar Interacting Random Systems

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WIAS Berlin