Donnerstag, 4. 12. 2008, 14:00 Uhr (ESH)
Prof. Ch. Geuzaine (University of Liege) and
Prof. J. F. Remacle (Universite catholique de Louvain)
Gmsh: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilitiesAbstract:
The development of Gmsh has been under way for a decade now. Recently, Gmsh has encountered a major evolution. In this talk, we will present Gmsh 2.0 and detail some of its innovative features: adaptive mesh generation algorithms applied to hybrid 3D models (STEP-IGES-Gmsh Native), mesh generation applied to ocean modelling, mesh reparametrization, and efficient visualization of high order finite element solutions.
Donnerstag, 16. 10. 2008, 14:00 Uhr (ESH)
E. Verbree (Delft University of Technology)
GIS-Technology: Spatial data handling of polyhedra through constrained Delaunay tetrahedralizationAbstract:
Closed, watertight, 3D geometries are represented by polyhedra. Current data models define these polyhedra basically as a set of polygons, leaving the test on intersecting polygons or open gaps to external validation rules. If this testing is not performed well, or not at all, non-valid polyhedra could be stored in geo-databases. We propose the utilization of the Constrained Delaunay Tetrahedralization (CDT) for the validation (i.e. check on self-intersecting and closeness) of polyhedra on the one hand, and the efficient storage of valid polyhedra on the other hand. The paper stresses on the decomposition of a polyhedron through a CDT and the possibility to compose the polyhedron through the vertices of the CDT, a bitmap that indicates which faces of the Delaunay Tetrahedralization (DT) links to a CDT-face, and a list of non-recovered CDT-faces.
Dienstag, 24. 06. 2008, 10:00 Uhr (ESH)
Prof. Dr. O. Iliev (Fraunhofer Institute for Industrial Mathematics (ITWM), Kaiserslautern)
On modeling and simulations of coupled flows in plain and porous mediaAbstract:
The talk concerns:
- macroscale modeling and simulation of single phase incompressible coupled flow in plain and in porous media,
- an approach for numerical upscaling of such flows, as well as
- some microscale simulations for two-phase flow in coupled plain and porous media flow.
In the first part of the presentation we will discuss the models for flow perpendicular to the porous medium, as well as for tangential flows. Interface conditions derived via homogenization, or via volume averaging, as well as the connection between them, will be presented. A finite volume numerical algorithm for solving such problems will be highlighted. In the above cases one inlet and one outlet is considered. In connection with some industrial processes, e.g., fuel cells, one has to consider also cases when there are two inlets and one outlet. Some microscopic simulation results for such problems will be presented and discussed. In the second part of the talk we will discuss an approach for numerical upscaling for coupled flows in the case of flow perpendicular to the porous medium. In this case Stokes-Brinkman system is upscaled to another Stokes-Brinkman system. The permeability at the macroscale is calculated by solving auxiliary cell problems, motivated by the homogenization approach.
Donnerstag, 05. 06. 2008, 14:00 Uhr (ESH)
Dr. J. Kulenkampff (Institut für Interdisziplinäre Isotopenforschung, Leipzig)
Prozesstomographie mit PET zur Ableitung von Transportparametern in GeomaterialienAbstract:
Positronen-Emissions-Tomographie als ursprünglich sehr effektives nuklearmedizinisches Bildgebungsverfahren eignet sich auch in besonderem Maße, um die Konzentration von Radiotracern während des Transports in Geomaterialien räumlich-zeitlich darzustellen. Bei extrem hoher Empfindlichkeit für die Tracerkonzentration (etwa 109 Atome/mm3) kann ein räumliches Auflösungsvermögen von etwa 1 mm erreicht werden. Bei der Bildrekonstruktion gibt es noch Optimierungsmöglichkeiten in Hinblick auf das dichte Material, beispielsweise bessere Korrekturen für Streuung und Absorption der Photonenstrahlung, deshalb treten noch einige Artefakte auf. Experimente mit Injektion eines Tracerpulses während der kontinuierlichen Durchströmung können zumindest qualitativ Aufschluss geben über präferentielle Fließpfade, Diffusion/Dispersion in das umgebende Material und Retention/Retardation der markierten Substanzen. Größerer Forschungsbedarf besteht auf dem Gebiet der Ableitung von Parametern zur Verteilung der Transportwege und Retentionszonen.
Dienstag, 22. 04. 2008, 14:30 Uhr (ESH)
Dr. W. D. Bessler (Ruprecht-Karls-Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen)
Elektrochemie und Transport in Feststoffoxid-Brennstoffzellen