Prof.
Wolfgang Bangerth
(Colorado State University)

23/07/2018, 09:00

deal.II is now 20 years old. I'll give a brief overview of how it started, how it has developed, and where I see it going in the future. This includes both the technical side and, in particular, the social side: deal.II is not just a software project, but also a community of developers and users.

Timo Heister
(Clemson University)

23/07/2018, 09:45

Multigrid methods are the only known approach to efficiently solve large
linear systems for solving PDEs by having runtime cost proportional to the
number of unknowns. Algebraic multigrid methods construct a hierarchy of
problems from the system matrix, while geometric multigrid methods use the
mesh hierarchy and system matrices from each level of this hierarchy.
While algebraic...

Mr
Sean McGovern
(Forschungszentrum Juelich)

23/07/2018, 11:20

Given the context of distributed parallelism, the purpose of this contribution is to consider a solution procedure to the classical Stefan phase change problem, an example of a free boundary problem. In the Stefan problem, the interface between water and ice moves through a domain as the ice melts due to a heat source. As an example of an interface problem, we choose to apply the level set...

Dr
Jean-Paul Pelteret
(Chair of Applied Mechanics, Friedrich-Alexander University Erlangen-Nuremberg)

24/07/2018, 09:00

In recent years there has been a notable growth in research among fields involving coupled media, and in multi-physics problems in general. As the complexity of the physics describing the material loading and response increases, so does the time cost and sophistication of the computational tools used to analyse these problems both in the academic and industrial settings. Associated with this...

Daniel Arndt
(University Heidelberg)

24/07/2018, 09:45

There are several different ways of describing bilinear forms in `deal.II`. All of these require to describe the assembly loop inside the program. This talk discusses an approach for providing the assembly operator from the outside using a domain-specific language.
In particular, this easily allows changing the backend used in the end. `CFL` also provides the possibility to generate the...

Dario Abbondanza
(Sapienza University of Rome)

24/07/2018, 11:00

It has been recently shown that a Diffuse Interface model is able to fully describe the dynamics of multiphase flows. In particular, the possibility of deriving a set of equations addressing the dynamic of the entire domain of simulation, makes it ideal to describe phenomena such as vapor bubble dynamics in a surrounding liquid. The model is able to capture surface tension effects, phase...

Mr
Benjamin Brands
(Friedrich-Alexander-Universität Erlangen-Nürnberg)

24/07/2018, 11:20

The mechanical response of magnetorheological composites is highly affected by an applied magnetic field. Since a generally valid constitutive law does not exist for such heterogeneous materials, multiscale techniques like computational homogenisation are commonly used to approximate effective macroscopic properties. In our approach the macroscopic quantities at a material point of a...

Dr
Nicola Giuliani
(SISSA)

24/07/2018, 11:40

During the last 8 years the mathLab laboratory at SISSA has analysed the swimming mechanisms of micro-organisms (unicellular beings as protists, algae or bacteria) both from a theoretical and an experimental point view. In this work we present a way to derive an accurate and reliable numerical setting for the resolution of general swimming mechanism. Such a framework can be seen as a numerical...

Mr
Nicola Giuliani
(SISSA)

25/07/2018, 09:45

Many modern 3D modelling tools offer the possibility of creating complex geometries in a very straightforward way (what is usually called creative freedom). Such softwares are extensively used in computer graphics (video-gaming, animation studios) and they are able to produce smooth surfaces exploiting the subdivision surface modelling which was derived by Edwin Catmull and Jim Clark in 1978...

Mr
Giovanni Alzetta
(SISSA)

25/07/2018, 11:00

I am beginning this talk with a quick recall of the general difficulties faced when using multiple grids on a distributed memory setting and some possible solutions.
As a model problem I am presenting briefly the Lagrange-multiplier method of step-60, where a harmonic equation with values prescribed at the boundary and on a sub-domain is solved, with a particular focus on the coupling matrix...

Michal Wichrowski
(Instytut Podstawowych Problemów Techniki)

25/07/2018, 11:20

The goal of my work is to develop robust scalable solver for linear system arising from finite element discretization of Stokes problem with strongly variable viscosity. Such linear systems appear in fluid-structure problems.
Symmetric positive define problems with discontinuous coefficient can be solved effectively by multigrid preconditioned Krylov subspace methods. Here we extend this...

Julius Witte
(Heidelberg University)

25/07/2018, 11:40

The goal of the ExaDG project is to provide efficient finite element solvers relying on `deal.II`'s `MatrixFree` framework based on higher order DG methods. However, the matrix-free operators restrict the choice of preconditioners. A powerful tool is offered by a geometric multigrid algorithm having a favorable linear complexity. The quality of multigrid preconditioners is crucially dependent...

Denis Davydov
(Friedrich-Alexander University Erlangen-Nuremberg)

26/07/2018, 09:00

Traditional solution approaches for problems in quantum mechanics scale as $\mathcal O(N^3)$, where $N$ is the number of electrons. Various methods have been proposed to address this issue and obtain linear scaling $\mathcal O(N)$. One promising formulation is the direct minimization of energy. Such methods take advantage of physical localization of the solution, namely that the solution can...

Dr
Wenyu Lei
(Texas A&M University)

26/07/2018, 09:45

In this talk, we propose a new nonconforming finite element algorithm to approximate a linear problem involving the integral fractional Laplacian. The method is based on the Dunford-Taylor integral representation of the bilinear form corresponding to the variational formulation. We obtain the approximated solution using the deal.II finite element library with a non-uniform mesh setting....

Prof.
Luca Heltai
(SISSA)

27/07/2018, 09:00

Version 9.0.0 of the `deal.II` library offers many new features and interfaces with several new external libraries.
In this talk I will provide an overview of some of the new features that I have contributed in adding to the library, including (in no particular order)
- Improved support for curved geometries
- Non-standard quadrature rules
- Improved support for user-defined...

Prof.
Luca Heltai
(SISSA),
Timo Heister
(Clemson University), Prof.
Wolfgang Bangerth
(Colorado State University)

27/07/2018, 12:30

Developers' track

Some conclusions and some plans for future developments and opportunities. In particular:
- How to attract funds to `deal.II`
- How to attract new users
- Open discussions on the best platforms for Forums/Discussions/Mailinglists
- Anything else

Dr
Andrea Mola
(SISSA)

Users' track

Contributed talks

To exploit the automated mesh generation and adaptive refinement capabilities offered by deal.II, the user must provide its program with a suitable description of the domain geometry. In particular, it is fundamental that the geometries of boundary and internal surfaces are available to the triangulation so that the nodes generated across each mesh refinement are placed onto such surfaces, in...