Suche
Anzeige der Dokumente 1-10 von 33
Konferenzveröffentlichung
The logarithmic finite element method
(International Center for Numerical Methods in Engineering (CIMNE), 2018)
The Logarithmic finite element (LogFE) method extends the Ritz-Galerkin method to approximations on a non-linear finite-dimensional manifold in the infinitedimensional solution space. Formulating the interpolant on the logarithmic space allows for a novel treatment of the rotational component of the deformation, and induces a strong coupling between rotations and translations. The Logarithmic finite element method provides
a transformation of the initial configuration that is not restricted to an isoparametric formulation.
Aufsatz
Introducing the Logarithmic finite element method: a geometrically exact planar Bernoulli beam element
(2016-09-15)
We propose a novel finite element formulation that significantly reduces the number of degrees of freedom necessary to obtain reasonably accurate approximations of the low-frequency component of the deformation in boundary-value problems. In contrast to the standard Ritz–Galerkin approach, the shape functions are defined on a Lie algebra—the logarithmic space—of the deformation function. We construct a deformation function based on an interpolation of transformations at the nodes of the finite element. In the case ...
Dissertation
Analysis and Projection of spatio-temporal Drought and Climate Change Impacts on Groundwater Resources and Surface-Groundwater Interactions for three Iranian Case Studies
(2018-08)
Der Klimawandel und deren Variabilität, wie z.B. die Dürre, wirken sich auf die Wasserressourcen und insbesondere auf die wertvolle Grundwasserressource aus, die im Iran mehr als 80% des Wasserbedarfs aller Bereiche (Landwirtschaft, Haushalt und Industrie) ausmacht. Es ist von größter Bedeutung, Anpassungsstrategien zur Bewältigung dieser Probleme zu finden, um ein nachhaltiges Wasserressourcenmanagement sicherzustellen. In dieser Hinsicht sind physikalisch basierte hydrologische Modelle gekoppelt mit Grundwassermodellen ...
Working paper
Ansatzfunktionen auf dem logarithmischen Raum: die Log-FE-Methode [Abstract]
(2015-09)
Die Logarithmische Finite-Elemente-Methode (Log-FE-Methode) bietet einen neuartigen Ansatz zur Berechnung von FE-Modellen, insbesondere im Rahmen von Multigrid-Verfahren.
In Multigrid-Verfahren wird eine schnelle und robuste Konvergenz insbesondere durch die Entkopplung der Einflüsse der Freiheitsgrade auf den unterschiedlichen Längenskalen erreicht. Das Näherungsverfahren auf dem groben Netz sollte daher auf einer deutlich gröberen Skala arbeiten und (räumlich) hochfrequente Deformationsanteile vermeiden.
Konferenzveröffentlichung
Beyond Ritz-Galerkin: Finite element approximations on a manifold in the configuration space [Abstract]
(Institute of Structural Analysis and Antiseismic Research, School of Civil Engineering, National Technical University of Athens (NTUA), 2016)
An extension of the Ritz-Galerkin method, based on finding approximations on a finite-dimensional manifold of functions (i.e., not a linear subspace) in the infinite-dimensional exact configuration space, will be presented. This new approach is particularly efficient in computing geometrically exact solutions for problems involving large rotations.
Konferenzveröffentlichung
Coupling atomistic models with continuous finite beam elements [Abstract]
(Institute of Structural Analysis and Antiseismic Research, School of Civil Engineering, National Technical University of Athens (NTUA), 2016)
Concurrent simulations of atomistic (discrete) and continuum models are one key to perform static calculations of large atomistic structures. Occurring ghost forces at the interfaces between discrete (atomistic) and continuous regions are a major challenge for the definition of such interfaces. The so called virtual projection method [1] is a class of force-based a/c schemes which reduce (or even avoid) ghost forces. This class of coupling schemes is able to deal with atomistic models consisting of bonded, multi-body ...
Dissertation
Die aeroelastische Stabilitätsanalyse – ein praxisnaher Ansatz zur intervalltheoretischen Betrachtung von Modellierungsunsicherheiten am Flugzeug
(2013-02-07)
Die Untersuchung des dynamischen aeroelastischen Stabilitätsverhaltens von Flugzeugen erfordert sehr komplexe Rechenmodelle, welche die wesentlichen elastomechanischen und instationären aerodynamischen Eigenschaften der Konstruktion wiedergeben sollen. Bei der Modellbildung müssen einerseits Vereinfachungen und Idealisierungen im Rahmen der Anwendung der Finite Elemente Methode und der aerodynamischen Theorie vorgenommen werden, deren Auswirkungen auf das Simulationsergebnis zu bewerten sind. Andererseits können die ...
Dissertation
Das Einzugsgebiet der Fulda - Untersuchung der Methoden der Hochwasserstatistik im Zeichen des Klimawandels
(2011-10-26)
Numerous studies have proven an effect of a probable climate change on the hydrosphere’s different subsystems. In the 21st century global and regional redistribution of water has to be expected and it is very likely that extreme weather phenomenon will occur more frequently. From a global view the flood situation will exacerbate. In contrast to these discoveries the classical approach of flood frequency analysis provides terms like “mean flood recurrence interval”. But for this analysis to be valid there is a need ...
Dissertation
Numerical Feasibility Study for Treated Wastewater Recharge as a Tool to Impede Saltwater Intrusion in the Coastal Aquifer of Gaza – Palestine
(2014-04-02)
The ongoing depletion of the coastal aquifer in the Gaza strip due to groundwater overexploitation has led to the process of seawater intrusion, which is continually becoming a serious problem in Gaza, as the seawater has further invaded into many sections along the coastal shoreline.
As a first step to get a hold on the problem, the artificial neural network (ANN)-model has been applied as a new approach and an attractive tool to study and predict groundwater levels without applying physically based hydrologic ...