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Colloquium

In this lecture series, leading researchers and promising young scientists report on their latest findings in the field of simulation technologies. We place particular emphasis on the interdisciplinary variety of contributions. We invite all interested parties to our Cluster Colloquium.

All colloquium dates for the Summer Term 2018

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Pattern Formation in Physical Systems: Modeling, Mathematics and Applications

Referent: Prof. Sanjay Govindjee, University of California, Berkeley

 

Time
April 18,  2018 04:00 pm
 
Auditorium 7.01, Pfaffenwaldring 7

 

Abstract of the presentation:

Nature and physical systems, in particular, are replete with patterns; simply think, for example, of the beatiful patterns, seen in snowflakes. These patterns appear on a multitude of scales and appear in many disparate physical systems. This gives rise to the thought that patterns as a phenomena should have a universal underlying model structure that can be used to describe what is observed in experiments. In this talk, I will present such a modeling concept that is found on the notion of energy minimization and minimizing sequences. The basis notions will be laid out in an introductory manner so as to be accessible to a broad audience. Example applications will be drawn primarily from the world of solid mechanics and material science, but others will be shown and discussed as time permits. The engineering exploitation and manupulation of patterns will also receive some attention.

 

Multiscale Simulation of Multiphase Materials

Referent: Prof. Dr.-Ing. Tim Ricken, University of Stuttgart

 

Time
April 25,  2018 04:00 pm
 
Auditorium 7.01, Pfaffenwaldring 7

 

Abstract of the presentation:

Many materials show a multiphase composition and have a distinct microscopic structure. Examples of multiphase materials are saturated or partly saturated porous materials like soil or concrete but also steel and biological tissue like cartilage or bone. Their substructures are e.g. pores, fibers with different orientations or cells which can be influenced by biochemical reactions.

The high complexity of these kinds of materials makes it reasonable to consider homogenization approaches and multiscale techniques in order to find an effective modeling access for the numerical simulation. This is even more the case since modern experimental methods as CT-scanning or MRI imaging give us the opportunity to get a deep insight into the microscale structure.

We will thus present a combined multiphase-multiscale approach for the description of these kinds of materials. The method is based on the well-known Theory of Porous Media (TPM), a continuum mechanical homogenization approach based on the mixture theory in combination with the concept of volume fraction, cf. [1, 2]. Depending on the material, we will combine the TPM with reasonable multiscale techniques such as FE2, POD-ODE, or the Phase Field Method [3, 4]. Examples of application are the description of microscale driven anisotropic perfusion of a porous material [5], the liver function-perfusion behavior [4,5,6], the steel solidification [7] or the biodegradation in porous landfill layers [8].

REFERENCES

[1] de Boer, R. (2000): Theory of Porous Media -- highlights in the historical development and current state: Springer-Verlag.

[2] Ehlers, W. (2002): Foundations of multiphasic and porous materials. In: W. Ehlers und J. Bluhm (Hg.): Porous media : theory, experiments and numerical applications: Springer-Verlag Berlin, Heidelberg, New York., S. 3–86.

[3] Moj, Lukas; Foppe, Manuel; Deike, Rüdiger; Ricken, Tim (2017): Micro-macro modelling of steel solidification. A continuum mechanical, bi-phasic, two-scale model including thermal driven phase transition. In: GAMM‐Mitteilungen 40 (2), S. 125–137. DOI: 10.1002/gamm.201720004.

[4] Christ, Bruno; Dahmen, Uta; Herrmann, Karl-Heinz; König, Matthias; Reichenbach, Jürgen R.; Ricken, Tim et al. (2017): Computational Modeling in Liver Surgery. In: Frontiers in Physiology 8, S. 906. DOI: 10.3389/fphys.2017.00906.

[5] Ricken, Tim; Waschinsky, Navina; Werner, Daniel (2018): Simulation of Steatosis Zonation in Liver Lobule—A Continuummechanical Bi-Scale, Tri-Phasic, Multi-Component Approach. In: Peter Wriggers, Prof. Thomas Lenarz (Hg.): Biomedical Technology. Modeling, Experiments and Simulation: Springer International Publishing.

[6] Pierce, David M.; Unterberger, Michael J.; Trobin, Werner; Ricken, Tim; Holzapfel, Gerhard A. (2016): A microstructurally based continuum model of cartilage viscoelasticity and permeability incorporating measured statistical fiber orientations. In: Biomechanics and Modeling in Mechanobiology 15 (1), S. 229–244. DOI: 10.1007/s10237-015-0685-x.

[7] Moj, Lukas; Foppe, Manuel; Deike, Rüdiger; Ricken, Tim (2017): Micro-macro modelling of steel solidification. A continuum mechanical, bi-phasic, two-scale model including thermal driven phase transition. In: GAMM‐Mitteilungen 40 (2), S. 125–137. DOI: 10.1002/gamm.201720004.

[8] Schulte, Marcel; Jochmann, Maik A.; Gehrke, Tobias; Thom, Andrea; Ricken, Tim; Denecke, Martin; Schmidt, Torsten C. (2017): Characterization of methane oxidation in a simulated landfill cover system by comparing molecular and stable isotope mass balances. In: Waste Management 69, S. 281–288. DOI: 10.1016/j.wasman.2017.07.032.

Smart Sensors as Multiphysics Problems - Why Modeling and Simulations are Crucial for Successful In-Situ Measurements

Referent: Prof. Dr. Jens Anders, University of Stuttgart

 

Time
Cancelled!
 

 

Abstract of the presentation:

Smart sensors in the broadest sense are sensors that are combined with dedicated hardware or software to produce a performance and/or functionality that goes greatly beyond that of the raw sensor. As such, smart sensors bear the potential to revolutionize all aspects of our everyday life, ranging from smart homes that benefit from ambient assisted living, optimized production lines in the frame of Industry 4.0 to high-end sensors that enable entirely new experiments in the scientific world.
In this talk, we will investigate the use of smart sensors in the latter field of high-end sensing for scientific applications and discuss how the multiphysics and advanced modeling aspects of state-of-the-art smart sensors are crucial for their performance.
To this end, we will discuss examples of biomedical quantum sensors that greatly benefit from the embedding of the interface electronics for enhanced performance. It will be discussed how an advanced modeling of the sensor together with a precise modeling of the interface electronics as nonlinear dynamical system can be used for co-designing sensor and electronics to improve the overall system performance. Finally, we will talk about the challenges in numerical simulations of such advanced sensor systems, which arise from the immense precision (often precisions of 10-9 or better are required) that is frequently required in the scientific context.

Wetting Fronts in Porous Media with Capillary Hysteresis and Dynamic Effects

Referent: Prof. Dr. Ir. C. J. van Dujin, Technical University Eindhoven

 

Time
June 27,  2018 3:00 pm
 
Auditorium 7.01, Pfaffenwaldring 7

 

Abstract of the presentation:

In this talk we consider in detail the behaviour of wetting fronts in the form of travelling wave solutions of Richards' equation, including the effect of capillary hysteresis and dynamic capillarity. With respect to the capillary hysteresis we discuss two models: (a) play-type hysteresis with vertical scanning curves and (b) extended play-type hysteresis with realistic (inclined) scanning curves. The dynamic effect is described by a capillarity coefficient and a non-constant capillarity function. Travelling waves describe well-developed saturation profiles that connect the injected saturation to the initial saturation. We discuss saturation overshoot, saturation bounds as well as the dependence of the saturation on the capillarity coefficient and capillarity function. We also present PDE simulations that confirm our theoretical findings.

Micro-Macro Models for Reactive Flow and Transport Problems in Complex Media

Referent: Prof. Dr. Peter Knabner, University of Erlangen-Nürnberg

 

Time
Cancelled!
 

 

Abstract of the presentation:

In porous media and other complex media with different length scales, (periodic) homogenization has been successfully applied for several decades to arrive at macroscopic, upscaled models, which only keep the microscopic information by means of a decoupled computation of “effective” parameters on a reference cell. The derivation of Darcy’s law for flow in porous media is a prominent example. Numerical methods for this kind of macroscopic models have been intensively discussed and in general are considered to be favourable compared to a direct microscale computation. On the other hand, if the interplay of processes becomes too complex, e.g. the scale seperation does not act in a proper way, the porous medium itself is evolving, ..., the upscaled models obtained may be micro-macro models in the sense, that the coupling of the macroscopic equations and the equations at the reference cell is both ways, i.e. at each macroscopic point a reference cell is attached and the solution in the reference cell depends on the macroscopic solution (at that point) and the macroscopic solution depends on the microscopic solutions in the reference cells. At the first glance such models seem to be numerically infeasible due to their enormous complexity ( in d+d spatial variables). If on the other hand this barrier can be overcome, micro-macro models are no longer a burden but a chance by allowing more general interaction of processes (evolving porous media, multiphase flow, general chemical reactions, ...), where the microscopic processes “compute” the constitutive laws, which need longer be assumed (similar to the concept of heterogeneous homogenization). We will discuss various examples and in particular numerical approaches to keep the numerical complexity in the range of pure macroscopic models.

 

 

Contact

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Barbara Teutsch

Coordinator Graduate School, Coach