Nonlinear fluid-structure interaction problem. Part I: implicit partitioned algorithm, nonlinear stability proof and validation examples

International audienceIn this work we consider the fluid-structure interaction in fully nonlinear setting, where different space discretization can be used. The model problem considers finite elements for structure and finite volume for fluid. The computations for such interaction problem are performed by implicit schemes, and the partitioned algorithm separating fluid from structural iterations. The formal proof is given to find the condition for convergence of this iterative procedure in the fully nonlinear setting. Several validation examples are shown to confirm the proposed convergence criteria of partitioned algorithm. The proposed strategy provides a very suitable basics for code-coupling implementation as discussed in Part II

Low Rank Approximation in Spectral Stochastic Finite Element method with Solution Space Adaption

Die Spektrale Stochastische Finite Elemente Methode (SSFEM) ist eine der bedeutendsten Verfahren zur Lösung partieller Differentialgleichungen mit stochastischen Parametern. In ihrer klassischen Form unterliegt sie dem Fluch der Dimension. Viele verschiedene Techniken wurden jüngst entwickelt, um dagegen zu steuern und so die Anwendbarkeit der SSFEM auch für hochdimensionale Probleme zu gewährleisten. Diese Techniken umfassen Niedrig-Rang Repräsentationen und eine Reduktion des Lösungsraumes. Wir präsentieren ein Verfahren mit einem schrittweisen Rang-1-Update basierend auf der Varitationsformulierung des Problems. Die resultierende Niedrig-Rang Repräsentation ist hinsichtlich der Energieminimierung zu gegebenem Rang nicht notwendigerweise optimal. Dieses Verfahren wird erweitert um eine optionale Anpassung des Lösungsraumes und der Möglichkeit eine optimale Niedrig-Rang Approximation durchzuführen.The Spectral Stochastic Finite Element Method (SSFEM) has become one of the most interesting methods in solving partial differential equations with stochastic parameters. In its classical form it underlies the Curse of Dimension. Many different techniques have been developed recently to go against that curse and consequently to make SSFEM applicable for high dimensional problems. These techniques include Low-Rank approaches and solution space reductions. We present a rank-one update scheme based on the variational formulation of the problem. The resulting Low-Rank representation is not necessarily an optimal one with respect to the minimum energy at the given rank. This scheme is extended to an optional solution space adaption and the possibility to compute an optimal decomposition

Nonlinear fluid-structure interaction problem. Part II: space discretization, implementation aspects, nested parallelization and application examples

International audienceThe main focus of the present article is the development of a general solution framework for coupled and/or interaction multi-physics problems based upon re-using existing codes into software products. In particular, we discuss how to build this software tool for the case of fluid-structure interaction problem, from finite element code Feap for structural and finite volume code OpenFOAM for fluid mechanics. This is achieved by using the Component Template Library (CTL) to provide the coupling between the existing codes into a single software product. The present CTL code-coupling procedure accepts not only different discretization schemes, but different languages, with the solid component written in Fortran and fluid component written in \Cpp. Moreover, the resulting CTL-based code also accepts the nested parallelization. The proposed coupling strategy is detailed for explicit and implicit fixed-point iteration solver presented in the Part I of this paper, referred to Direct Force-Motion Transfer/Block-Gauss-Seidel. However, the proposed code-coupling framework can easily accommodate other solution schemes. The selected application examples are chosen to confirm the capability of the code-coupling strategy to provide a quick development of advanced computational tools for demanding practical problems, such as 3D fluid models with free-surface flows interacting with structures

A surrogate model for data-driven magnetic stray field calculations

In this contribution we propose a data-driven surrogate model for the prediction of magnetic stray fields in two-dimensional random micro-heterogeneous materials. Since data driven models require thousands of training data sets, FEM simulations appear to be too time consuming. Hence, a stochastic model based on Brownian motion, which utilizes an efficient evaluation of stochastic transition matrices, is applied for the training data generation. For the encoding of the microstructure and the optimization of the surrogate model, two architectures are compared, i.e. the so-called UResNet model and the Fourier Convolutional neural network (FCNN). Here we analyze two FCNNs, one based on the discrete cosine transformation and one based on the complex-valued discrete Fourier transformation. Finally, we compare the magnetic stray fields for independent microstructures (not used in the training set) with results from the FE$^2$ method, a numerical homogenization scheme, to demonstrate the efficiency of the proposed surrogate model

Experimental and numerical investigations of the development of residual stresses in thermo-mechanically processed Cr-alloyed steel 1.3505

Residual stresses in components are a central issue in almost every manufacturing process, as they influence the performance of the final part. Regarding hot forming processes, there is a great potential for defining a targeted residual stress state, as many adjustment parameters, such as deformation state or temperature profile, are available that influence residual stresses. To ensure appropriate numerical modeling of residual stresses in hot forming processes, comprehensive material characterization and suitable multiscale Finite Element (FE) simulations are required. In this paper, experimental and numerical investigations of thermo-mechanically processed steel alloy 1.3505 (DIN 100Cr6) are presented that serve as a basis for further optimization of numerically modeled residual stresses. For this purpose, cylindrical upsetting tests at high temperature with subsequently cooling of the parts in the media air or water are carried out. Additionally, the process is simulated on the macroscale and compared to the results based on the experimental investigations. Therefore, the experimentally processed specimens are examined regarding the resulting microstructure, distortions, and residual stresses. For the investigation on a smaller scale, a numerical model is set up based on the state-data of the macroscopic simulation and experiments, simulating the transformation of the microstructure using phase-field theory and FE analysis on micro- and meso-scopic level

Cross-Sectional Associations between Homoarginine, Intermediate Phenotypes, and Atrial Fibrillation in the CommunityThe Gutenberg Health Study

Homoarginine has come into the focus of interest as a biomarker for cardiovascular disease. Atrial fibrillation (AF) causes a substantial increase in morbidity and mortality. Whether circulating homoarginine is associated with occurrence or persistence of AF and may serve as a new predictive biomarker remains unknown. We measured plasma levels of homoarginine in the population-based Gutenberg health study (3761 patients included, of them 51.7% males), mean age 55.6 +/- 10.9 years-old. Associations between homoarginine and intermediate electrocardiographic and echocardiographic phenotypes and manifest AF were examined. Patients with AF (124 patients, of them 73.4% males) had a mean age 64.8 +/- 8.6 years-old compared to a mean age of 55.3 +/- 10.9 in the population without AF (p-value < 0.001) and showed a less beneficial risk factor profile. The median homoarginine levels in individuals with and without AF were 1.9 mol/L (interquartile range (IQR) 1.5-2.5) and 2.0 mol/L (IQR 1.5-2.5), respectively, p = 0.56. In multivariable-adjusted regression analyses homoarginine was not statistically significantly related to electrocardiographic variables. Among echocardiographic variables beta per standard deviation increase was -0.12 (95% confidence interval (CI) -0.23-(-0.02);p = 0.024) for left atrial area and -0.01 (95% CI -0.02-(-0.003);p = 0.013) for E/A ratio. The odds ratio between homoarginine and AF was 0.91 (95% CI 0.70-1.16;p = 0.45). In our large, population-based cross-sectional study, we did not find statistically significant correlations between lower homoarginine levels and occurrence or persistence of AF or most standard electrocardiographic phenotypes, but some moderate inverse associations with echocardiographic left atrial size and E/A. Homoarginine may not represent a strong biomarker to identify individuals at increased risk for AF. Further investigations will be needed to elucidate the role of homoarginine and cardiac function

Related research data to "A surrogate model for data-driven magnetic stray field calculations"

This dataset contains the input of the model for neural network with a UResNet architecture for application as surrogate model for the prediction of magnetic stray fields in two-dimensional random micro-heterogeneous materials. It consist of a colletion of 500 files of two-dimensional binary image data, in which a pixel with a value of 0 (1) corresponds to the magnetic solid (vacuum space), of the size of 128x128 pixel. As well included is short description of the applied configuration of the UResNet used in the related publication. The uploads are provided as exports from the shared electronic lab notebook (ELN) instance in .eln format (fully .zip archive compatible).1.

CRC/TRR 270 Z-INF - Inside a multidisciplinary joint project

Poster über das Z-INF Projekt des SFB/TRR 270 HoMMage, präsentiert auf dem HeFDI Plenary 2020

Code-coupling strategy for efficient development of computer software in multiscale and multiphysics nonlinear evolution problems in computational mechanics

International audienc