Leibniz MMS Days 2022
The Leibniz Network "Mathematical Modeling and Simulation" carried out the fifth Leibniz MMS Days hosted by the Potsdam Institute for Climate Impact Research (PIK). The Workshop aimed to further develop the MMS networking activities in the different Institutes, presenting undergoing work using modern methods of MMS and creating a plattform for discussion on themes of specific and general interest.
DOI (Serie): 10.5446/s_1243
22
2022
252
12 Stunden 39 Minuten
22 Ergebnisse
48:10
8Pfeiffer, HaraldSeveral times per hour, a pair of black holes coalesces somewhere in the observable Universe. Direct supercomputer calculations of binary black holes elucidate the dynamics of warped space-time and underpin gravitational wave observations of these systems. This talk introduces the techniques of such simulations and their application to gravitational wave astronomy. We summarize current observational results and future challenges.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
22:00
4Zahn, StefanDeep eutectic solvents are liquids composed of two compounds with a significant melting point depression. Most popular are mixtures of choline chloride, a provitamin produced on the megaton scale. Deep eutectic solvents composed of polymerizable compounds allow frontal polymerization at low temperature and with full conversion and thus, unique functional coatings can be obtained. To understand the origin of non-ideal mixing behavior of deep eutectic solvents, we have investigated a homologous series of choline chloride by molecular dynamics simulations. We found that the incorporation of the anion into the hydrogen bond network plays a central role for the observed properties. Additionally, we will present a polarizable force field developed to study the ion correlation in these liquids.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
36:23
8Miller, WolframKinetic Monte Carlo is a nice tool to study the growth kinetics of epitaxial processes on an atomistic scale. However, energy barriers for the various surface processes must be defined and thus either data from ab initio calcalutions or from dedicated experiments are required. Furthermore, processes can be handled only successively so that there is no natural way for parallization. We show two application cases: homoepitaxy of Ga2O3 and epitaxy of AlN or AlGaN on AlN. The specific numerical issues for the computation will be addressed.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
44:05
27Marquardt, OliverSemiconductor heterostructures represent key ingredients for application in novel light emitters and detectors, energy harvesting, or quantum technology. Numerical simulations of the optoelectronic properties of heterostructures such as thin films, nanowires, and quantum dots facilitate both a detailed and systematic understanding of observations from experiment as well as theory-guided design of nanostructures such that they fulfill the requirements of a specific application. We will provide an overview of our modelling capabilities of the electronic properties of semiconductor heterostructures using continuum-based multiband k.p models, implemented within the plane-wave framework of the SPHInX library [1,2]. We illustrate the applicability of our approach by showcasing some recent example studies [3]. 1: sxrepo.mpie.de 2: S. Boeck et al., Computer Phys. Commun. 182, 543 (2011) 3: O. Marquardt, Comp. Mat. Sci. 194, 110318 (2021)
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
34:56
3Wolfrum, MatthiasWe investigate the synchronization transitions in systems of coupled Kuramoto-Sakaguchi phase oscillators. We show that in globally coupled systems with certain unimodal frequency distributions, there can appear unusual types of synchrony transitions, where synchrony can decay with increasing coupling, incoherence can regain stability for increasing coupling, or multistability between partially synchronized states and/or the incoherent state can appear. In one-dimensional arrays of oscillators with non-local coupling one can observe at the onset of synchrony the emergence of collective macroscopic chaos as an intermediate stage between complete incoherence and stable partially coherent plane waves. In both cases, the phase lag in the interaction function plays an important role for the observed phenomena.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
33:22
2Plietzsch, AntonFuture power grids will be operating a large number of heterogeneous dynamical actors. Many of these will contribute to the fundamental dynamical stability of the system, and play a central role in establishing the self-organized synchronous state that underlies energy transport through the grid. We derive a normal form for grid forming components in power grids, that allows analyzing the grids systemic properties in a technology neutral manner, without detailed component models. We provide a first experimental validation that this normal form can capture the behavior of complex grid forming inverters without any knowledge of the underlying technology, and show that it can be used to make technology independent statements on the stability of future grids.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
31:41
6Küker, ManfredMean field magnetohydrodynamics is a theoretical framework that uses averaged versions of the induction equation and the equation of motion to model large-scale gas flows and the generation of large-scale magnetic fields in astrophysical bodies. This method is computationally cheap and has been used with some success in astrophysics but requires a theory of the effect of the small scale gas motions on the large scale motions and magnetic field. More recently, advances in high performance computing have made direct numerical simulations feasible. We show results from both approaches.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
28:04
12Frerichs-Mihov, DerkApproximating the solution of convection-diffusion equations in the convection-dominated regime by standard methods usually lead on affordable grids to unphysical values, so called spurious oscillations. Standard discontinuous Galerkin methods are known on the one hand to produce sharp layers but on the other hand are also not able to prevent the pollution of the solution. This talk introduces a post-processing method that uses so called slope limiter to automatically detect regions where the solution is polluted and to correct the solution in these regions. Several slope limiting techniques are presented and tested on two standard benchmark problems.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
28:30
6Giefer, PatrickEmulsions are widely used in a variety of different industries and applications with increasing importance. Two main objectives need to be addressed in the emulsion formulation: The emulsion needs to be formed with a narrow and predefined size distribution and it needs to be stabilized to prevent coalescence and therefore facilitate handling of the emulsion. So far the breakup mechanism of droplets in Membranes is still unknown. Further the role of proteins on breakup mechanism due to their interfacial adsorption and induces change in wettability needs to be addressed. In this work Molecular Dynamic simulations were performed to give an insight on protein adsorption to oil/water and water/SIO2 interfaces to understand which role Proteins play in this context. Furthermore Computational Fluid Dynamics were conducted to clarify the breakup mechanism in capillary confinements under varying fluid properties as well as membrane wettability. The results show that the proteins not only adsorb to fluid/fluid but also fluid/solid interfaces and therefore change the properties of the membrane. From the fluid-dynamic perspective membrane wettability plays a major role on the droplet dispersion as well as in the emergence of fluid dynamic instabilities that eventually lead to breakup.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
32:23
6Jahnel, BenediktSpatial device-to-device communications are expected to play a key role in future communication systems. Their often high complexity can, at least in part, be modelled with the help of a probabilistic approach, where the network components are considered to be a stochastic point process. In this talk, I will introduce some of the most important ingredients in the theory of stochastic geometry, and present examples on how we use them to study for example malware propagation in device-to-device networks or bottleneck behavior for the connectivity in such networks.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
36:16
8Dörfler, FlorianFirst 2:38 minutes of video does not have audio.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
32:24
Stegmüller, JohannesThe number of scientific publications containing mathematical expressions is immense and constantly growing. For example, zbMATH Open, the world's longest-running abstracting and review service for mathematical content, indexes over 160 million formulas. Mathematical formula search is a core technology for finding scientific documents where formulas are defined as input. Since the introduction of many mathematical search systems in the NTCIR Math-Task series from 2013, there have been further advances and implementations of formula search. In the first 15 minutes of our talk, we want to provide an overview of current methods of formula search and related applications. According to the FAIR principles, we will emphasize aspects of reusability and accessibility here. Then, for the next 10 minutes, we intend to reach out to the audience and have a lively discussion on the planned efforts and experiences of the community with formula search.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
18:06
12Nolte, DavidMathematical research data (MRD), arising in many scientific fields, encompass widely different types of data and can be vast and complex, e.g., numerical data sets, mathematical expressions, algorithms, etc. The NFDI MRD Initiative (MaRDI) aims to define standards for MRD, to design verifiable workflows and to provide services to the scientific community. The services will be bundled in a web portal, allowing researchers to easily find and access mathematical research data, knowledge and services. In addition, the portal will offer storage capacities and host services for workflow and algorithm execution. At the core of the portal lies a mathematical knowledge graph which organizes and interconnects data from multiple sources. The main contribution of the portal is providing a unified entry point to access scattered and unconnected data. This talk gives an overview of the current status and planned features of the portal, and its value for the mathematical community.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
36:02
12May, DavidFiber reinforced polymers (FRPs) are ideal lightweight materials that can play a key role in, sustainable mobility, harvesting of natural energy resources, assisted living, and cutting edge medical technologies. However, high production costs are often still a main obstacle for broad industrial application. Robust design of the manufacturing processes and efficient analysis methods are an essential requirements in order to achieve economical implementation. Today, this is usually enabled by numerical simulations of the material behavior and their manufacturing processes. In this keynote talk, we showcase the areas of fiber reinforced polymer composites where numerical simulations have been implemented in order to gain a deeper understanding into their processing and physical behavior. From simulations of FRP manufacturing processes, to virtual material characterization at the micro and meso-scale as well the design of smart structures and their analyses using novel techniques.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
36:30
4Gressel, OliverThe interstellar medium of the Milky Way and nearby disk galaxies harbours large-scale coherent magnetic fields of Microgauss strength, that can be explained via the action of a mean-field dynamo. As in our previous work, we aim to quantify dynamo effects that are self-consistently emerging in realistic direct magnetohydrodynamic simulations, but we generalise our approach to the case of a non-local (non-instantaneous) closure relation, described by a convolution integral in space (time). To this end, we leverage our comprehensive simulation framework for the supernova-regulated turbulent multi-phase interstellar medium. By introducing spatially (temporally) modulated mean fields, we extend the previously used test-field method to the spectral realm -- providing the Fourier representation of the convolution kernels. The resulting spectra of the dynamo mean-field coefficients that we obtain broadly match expectations and allow to rigorously constrain the degree of scale separation in the Galactic dynamo.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
30:13
13Graefe, JanThe efficiency of heat and mass exchange between leaves and their environment under low wind speed is dominated by free convection. This is commonly quantified in terms of the Nusselt number (Nu) and the Rayleigh number (Ra). The currently available Nu = f(Ra) relations for inclined plates were mostly derived for infinite wide plates or from one-sided heat transfer studies. A comprehensive simulated data set of laminar free convection may be used to derive new Nu relations at any inclination and for both plate sides. The relevant equations for free convection in 3D are solved numerically using the computational fluid dynamic (CFD) software OpenFOAM. The simulated Nusselt numbers agree very good with previous measurements for vertical and horizontal circular plates having a diameter of 84 mm. Various finite thickness (0.5 mm) elliptical plates (i.e. leaves) having aspect ratios between 1 and 3, plate length ranging from 30 to 160 mm and a range of inclinations are simulated with plate to air differences set to 1?12 K. Simulated heat fluxes from each leaf side are used to parameterize a comprehensive set of Nu relations.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
47:30
80Fuhrmann, JürgenThe Julia programming language is gaining increasing attraction in scientific computing, data analysis, machine learning and other fields. Some of its outstanding features are: - open source license - easy-to-learn syntax - powerful abstractions and generic programming features - high performance potential due to just-in-time compiling - extensibility and reproducibility via sophisticated package management - portability among operating systems - re-use of existing codebase via interfaces to other languages The talk provides an example-based introduction into Julia and some of its basic concepts and discusses examples where recent research at WIAS was able to take advantage of Julia.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
30:09
15Jalali, AliTemperature is one of the most important factors affecting quality and shelf life of fresh fruits and vegetables. Fresh produce is exposed to changing temperature conditions during the supply chain. This makes a big challenge in designing storage transport containers, which are supposed to provide optimum modified gas concentration inside. In this study, a system was developed to actively control CO2 and O2 concentrations inside a storage container under constant and changing temperature. A mini blower exchanging air between the container and external atmosphere controlled the internal gas concentration. This was done with the help of a thin and long tube, which prevented air from entering the container but facilitated air exchange when the blower is switched ON. The Blower ON Frequency (s h-1) was modelled as a function of storage temperature, taking the type and amount of fruit, blower and tube properties and the set point of O2 volumetric concentration into account. The model was then used in programming an Arduino microcontroller to control the blower in response to real-time measurement of storage temperature. The developed gas control system was then validated by storage of sweet cherries. The system could control the CO2 concentration at the set point level (12.5 ?for constant temperatures of 6 °C and 17 °C and changing temperature from 17 °C to 9 °C by applying the required Blower ON Frequency. There was a good agreement between the measured values of gas concentration and predicted values from the simulation so that the maximum RMSE value of predictions was 0.24 ?elated to O2 at changing temperature condition.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
50:09
11Rezzolla, LucianoI will briefly discuss how the first image of a black hole was obtained by the EHT collaboration. In particular, I will describe the theoretical aspects that have allowed us to model the dynamics of the plasma accreting onto the black hole and how such dynamics was used to generate synthetic black-hole images. I will also illustrate how the comparison between the theoretical images and the observations has allowed us to deduce the presence of a black hole in M87 and to extract information about its properties. Finally, I will describe the lessons we have learned about strong-field gravity and alternatives to black holes.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
34:57
5Knoth, OswaldThere is ongoing work worldwide to write new dynamical cores for numerical weather prediction. The reasons are simple refactoring, take into account new processor architectures, try new programming environments, and finally use latest achievements in numerical mathematics. I will summarize actual developments and show some examples from my own personal endeavor within the Climate Modeling Alliance (https://clima.caltech.edu/). Here we develop a new numerical core using the programming language Julia for a new earth system model which should learn from different data sources. The new dynamical core is based on a cubed sphere grid with high order continuous or discontinuous ansatz functions. To understand stability issues I have implemented standard test cases in the DG code FLUXO. Here the same stability issues were observed but could be resolved with a so called split-form kinetic energy conserving formulation. For a second planned formulation with continuous elements I have implemented my algorithm version in Matlab and subsequently in Julia. By means of the Held-Suarez example we will compare implementation details to get efficiency for both programming environments and present a new Rosenbrock-W-method where the explicit part has the strong stability preservation (SSP) property.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
33:06
5Hellmann, FrankModern power grids are among the crowning engineering achievements of mankind. They are complex, self-organizing continental size machines that work incredibly reliably. The energy transition requires a live restructuring of this machine in the middle of ongoing operation. Taking a theoretical physics / complexity theoretic view I review a number of ways in which the tools of complexity science: network theory, probabilistic reasoning and data-driven modeling, can help.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.
34:22
5Janke, David et al.Agriculture is a major emitter of particulate matter (PM), which causes health problems and can act as a carrier of the pathogen material that spreads diseases. The aim of this study was to investigate an open-source solver that simulates the transport and dispersion of PM for typical agricultural applications. We investigated a coupled Eulerian?Lagrangian solver within the open source software package OpenFOAM. The continuous phase was solved using transient large eddy simulations, where four different subgrid-scale turbulence models and an inflow turbulence generator were tested. The discrete phase was simulated using two different Lagrangian solvers. For the validation case of a turbulent flow of a street canyon, the flowfield could be recaptured very well, with errors of around 5?or the non-equilibrium turbulence models (WALE and dynamicKeq) in the main regions. The inflow turbulence generator could create a stable and accurate boundary layer for the mean vertical velocity and vertical profile of the turbulent Reynolds stresses R11. The validation of the Lagrangian solver showed mixed results, with partly good agreements (simulation results within the measurement uncertainty), and partly high deviations of up to 80?or the concentration of particles. The higher deviations were attributed to an insufficient turbulence regime of the used validation case, which was an experimental chamber. For the simulation case of PM dispersion from manure application on a field, the solver could capture the influence of features such as size and density on the dispersion. The investigated solver is especially useful for further investigations into time-dependent processes in the near-source area of PM sources.
2022Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) et al.