13 Zentrale Universitätseinrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/14
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Item Open Access Performance comparison of CFD microbenchmarks on diverse HPC architectures(2024) Galeazzo, Flavio C. C.; Garcia-Gasulla, Marta; Boella, Elisabetta; Pocurull, Josep; Lesnik, Sergey; Rusche, Henrik; Bnà, Simone; Cerminara, Matteo; Brogi, Federico; Marchetti, Filippo; Gregori, Daniele; Weiß, R. Gregor; Ruopp, AndreasOpenFOAM is a CFD software widely used in both industry and academia. The exaFOAM project aims at enhancing the HPC scalability of OpenFOAM, while identifying its current bottlenecks and proposing ways to overcome them. For the assessment of the software components and the code profiling during the code development, lightweight but significant benchmarks should be used. The answer was to develop microbenchmarks, with a small memory footprint and short runtime. The name microbenchmark does not mean that they have been prepared to be the smallest possible test cases, as they have been developed to fit in a compute node, which usually has dozens of compute cores. The microbenchmarks cover a broad band of applications: incompressible and compressible flow, combustion, viscoelastic flow and adjoint optimization. All benchmarks are part of the OpenFOAM HPC Technical Committee repository and are fully accessible. The performance using HPC systems with Intel and AMD processors (x86_64 architecture) and Arm processors (aarch64 architecture) have been benchmarked. For the workloads in this study, the mean performance with the AMD CPU is 62% higher than with Arm and 42% higher than with Intel. The AMD processor seems particularly suited resulting in an overall shorter time-to-solution.Item Open Access Investigations of metallurgical differences in AISI 347 and their influence on deformation and transformation behaviour and resulting fatigue life(2024) Veile, Georg; Regitz, Elen; Smaga, Marek; Weihe, Stefan; Beck, TillmannDue to variations in chemical composition and production processes, homonymous austenitic stainless steels can differ significantly regarding their initial microstructure, metastability, and thus, their fatigue behavior. Microstructural investigations and fatigue tests have been performed in order to evaluate this aspect. Three different batches and production forms of nominally one type of steel AISI 347 were investigated under monotonic tensile tests and cyclic loading under total strain and stress control in low and high cycle fatigue regimes, respectively. The deformation induced α’-martensite formation was investigated globally by means of in situ magnetic measurements and locally using optical light microscopy of color etching of micrographs. The investigation showed that the chemical composition and the different production processes influence the material behavior. In fatigue tests, a higher metastability and thus a higher level of deformation induced α’-martensite pronounced cyclic hardening, resulting in significantly greater endurable stresses in total strain-controlled tests and an increase in fatigue life in stress-controlled tests. For applications of non-destructive-testing, detailed knowledge of a component’s metastability is required. In less metastable batches and for lower stress levels, α’-martensite primarily formed at the plasticization zone of a crack. Furthermore, the formation and nucleation points of α’-martensite were highly dependent on grain size and the presence of δ-ferrite. This study provides valuable insights into the different material behavior of three different batches with the same designation, i.e., AISI 347, due to different manufacturing processes and differences in the chemical composition, metastability, and microstructure.Item Open Access An innovative technological infrastructure for managing SARS-CoV-2 data across different cohorts in compliance with General Data Protection Regulation(2024) Dellacasa, Chiara; Ortali, Maurizio; Rossi, Elisa; Abu Attieh, Hammam; Osmo, Thomas; Puskaric, Miroslav; Rinaldi, Eugenia; Prasser, Fabian; Stellmach, Caroline; Cataudella, Salvatore; Agarwal, Bhaskar; Mata Naranjo, Juan; Scipione, GabriellaBackground: The ORCHESTRA project, funded by the European Commission, aims to create a pan-European cohort built on existing and new large-scale population cohorts to help rapidly advance the knowledge related to the prevention of the SARS-CoV-2 infection and the management of COVID-19 and its long-term sequelae. The integration and analysis of the very heterogeneous health data pose the challenge of building an innovative technological infrastructure as the foundation of a dedicated framework for data management that should address the regulatory requirements such as the General Data Protection Regulation (GDPR). Methods: The three participating Supercomputing European Centres (CINECA - Italy, CINES - France and HLRS - Germany) designed and deployed a dedicated infrastructure to fulfil the functional requirements for data management to ensure sensitive biomedical data confidentiality/privacy, integrity, and security. Besides the technological issues, many methodological aspects have been considered: Berlin Institute of Health (BIH), Charité provided its expertise both for data protection, information security, and data harmonisation/standardisation. Results: The resulting infrastructure is based on a multi-layer approach that integrates several security measures to ensure data protection. A centralised Data Collection Platform has been established in the Italian National Hub while, for the use cases in which data sharing is not possible due to privacy restrictions, a distributed approach for Federated Analysis has been considered. A Data Portal is available as a centralised point of access for non-sensitive data and results, according to findability, accessibility, interoperability, and reusability (FAIR) data principles. This technological infrastructure has been used to support significative data exchange between population cohorts and to publish important scientific results related to SARS-CoV-2. Conclusions: Considering the increasing demand for data usage in accordance with the requirements of the GDPR regulations, the experience gained in the project and the infrastructure released for the ORCHESTRA project can act as a model to manage future public health threats. Other projects could benefit from the results achieved by ORCHESTRA by building upon the available standardisation of variables, design of the architecture, and process used for GDPR compliance.Item Open Access Impact of wind pressure coefficients on the natural ventilation effectiveness of buildings through simulations(2024) Sakiyama, Nayara Rodrigues Marques; Carlo, Joyce Correna; Sakiyama, Felipe Isamu Harger; Abdessemed, Nadir; Frick, Jürgen; Garrecht, HaraldNatural Ventilation Effectiveness (NVE) is a performance metric that quantifies when outdoor airflows can be used as a cooling strategy to achieve indoor thermal comfort. Based on standard ventilation threshold and building energy simulation (BES) models, the NVE relates available and required airflows to quantify the usefulness of natural ventilation (NV) through design and building evaluation. Since wind is a significant driving force for ventilation, wind pressure coefficients (Cp) represent a critical boundary condition when assessing building airflows. Therefore, this paper investigates the impact of different Cp sources on wind-driven NVE results to see how sensitive the metric is to this variable. For that, an experimental house and a measurement period were used to develop and calibrate the initial BES model. Four Cp sources are considered: an analytical model from the BES software (i), surface-averaged Cp values for building windows that were calculated with Computational Fluid Dynamics (CFD) simulations using OpenFOAM through a cloud-based platform (iia,b,c), and two databases-AIVC (iii) and Tokyo Polytechnic University (TPU) (iv). The results show a variance among the Cp sources, which directly impacts airflow predictions; however, its effect on the performance metric was relatively small. The variation in the NVE outcomes with different Cp’s was 3% at most, and the assessed building could be naturally ventilated around 75% of the investigated time on the first floor and 60% in the ground floor spaces.Item Open Access Kultureller Wandel(2024) Becker, Laura; Hornyak, Harald; Kettelhack, Julia; Löffler, Susanne; Petersen, Timo; Steinwand, Melanie; Trötschel, Tanja; Waller, Helmut; Wannagat, Christin; Wetzel-Vollmer, MarenDie digitale Arbeit verändert unsere Arbeitswelt, nicht nur punktuell, sondern grundlegend. Zwar hat es immer schon Veränderungen gegeben, dass diese sich aber so schnell und kaum mehr absehbar vollziehen, ist neu und stellt die Gesellschaft insgesamt vor große Herausforderungen. Dass diese Herausforderungen zudem in eine Zeit fallen, die durch allgemeine Verunsicherung durch Klimakrise, Kriege, nachlassendes wirtschaftliches Wachstum und gesellschaftliche Polarisierung charakterisiert ist, führt in der Wahrnehmung der Autor*innen des vorliegenden White Papers zu unterschiedlichen Reaktionen: Die einen nehmen diese Herausforderungen als Teil einer umfassenden allgemeinen Krise wahr, resignieren oder stemmen sich allem Neuen entgegen. Andere sehen in diesen Herausforderungen der Arbeitswelt auch eine Chance, die ihnen konkrete Handlungsmöglichkeiten eröffnet und Verbesserungen ermöglicht. Als Ergebnis des Think Tanks TT09 „Kultureller Wandel“ der Landesinitiative baden-württembergischer Universitäten bwUni.digital zeigen die Autor*innen dieses White Papers für Hochschulleitungen sowie für Organisations- und Personalentwickler*innen Maßnahmen der Kulturdiagnostik und Kulturentwicklung sowie konkrete Handlungsempfehlungen für eine erfolgreiche Transformationsbegleitung auf. Mit dem White Paper wird damit der bisherige Besprechungskatalog von bwUni.digital, u.a. zur Struktur und Strategie digitalisierter administrativer Prozesse, nun auch um das Thema der sozialen Akzeptanz durch einen kulturellen Wandel vervollständigt. Denn Dreh- und Angelpunkt für eine erfolgreiche Transformation, ob digital oder nicht, sind und bleiben die Organisationskultur und ihre Veränderungsfähigkeit.Item Open Access Every thing can be a hero! : narrative visualization of person, object, and other biographies(2024) Kusnick, Jakob; Mayr, Eva; Seirafi, Kasra; Beck, Samuel; Liem, Johannes; Windhager, FlorianKnowledge communication in cultural heritage and digital humanities currently faces two challenges, which this paper addresses: On the one hand, data-driven storytelling in these fields has mainly focused on human protagonists, while other essential entities (such as artworks and artifacts, institutions, or places) have been neglected. On the other hand, storytelling tools rarely support the larger chains of data practices, which are required to generate and shape the data and visualizations needed for such stories. This paper introduces the InTaVia platform, which has been developed to bridge these gaps. It supports the practices of data retrieval, creation, curation, analysis, and communication with coherent visualization support for multiple types of entities. We illustrate the added value of this open platform for storytelling with four case studies, focusing on (a) the life of Albrecht Dürer (person biography), (b) the Saliera salt cellar by Benvenuto Cellini (object biography), (c) the artist community of Lake Tuusula (group biography), and (d) the history of the Hofburg building complex in Vienna (place biography). Numerous suggestions for future research arise from this undertaking.Item Open Access Particle-resolved simulation of the pyrolysis process of a single plastic particle(2024) Zhang, Feichi; Tavakkol, Salar; Galeazzo, Flavio C. C.; Stapf, DieterParticle-resolved simulations have been performed to study the pyrolysis process of a high-density polyethylene (HDPE) particle in an inert hot nitrogen flow. The simulations resolve the velocity and temperature boundary layers around the particle, as well as the gradients of temperature and concentration within the particle. The objective of this work is to gain an in-depth understanding of the effect of particle morphology-specifically, the particle size and shape-on the interplay between heat transfer and pyrolysis progress, as well as to assess the applicable particle size when using the Lagrangian concept for simulating plastic pyrolysis. In all simulation cases, the pyrolysis reaction is initiated at the external surface of the particle, where the particle is heated the fastest. The reaction front propagates inward toward the core of the particle until it is fully pyrolyzed. For particle diameters larger than 4 mm, distinct temperature gradients within the particle can be detected, leading to a temperature difference of more than 10 K between the core and the external surface of the plastic particle. In this case, the Lagrangian simulations yield a considerably slower conversion compared with the particle-resolved simulations. Moreover, the cylindrical particle in longitudinal flow has been found to be pyrolyzed more slowly compared with the spherical and shell-shaped particles, which is attributed to the enhanced heat transfer conditions for the cylindrical particle. The results reveal the importance of considering particle morphology when modeling plastic pyrolysis. In addition, the Lagrangian approach, which assumes particle homogeneity, is only applicable for particle diameters smaller than 2 mm when modeling plastic pyrolysis.Item Open Access Coherent mesh representation for parallel I/O of unstructured polyhedral meshes(2024) Weiß, R. Gregor; Lesnik, Sergey; Galeazzo, Flavio C. C.; Ruopp, Andreas; Rusche, HenrikThis paper presents a new mesh data layout for parallel I/O of linear unstructured polyhedral meshes. The new mesh representation infers coherence across entities of different topological dimensions, i.e., grid cells, faces, and points. The coherence due to cell-to-face and face-to-point connectivities of the mesh is formulated as a tree data structure distributed across processors. The mesh distribution across processors creates consecutive and contiguous slices that render an optimized data access pattern for parallel I/O. A file format using the coherent mesh representation, developed and tested with OpenFOAM, enables the usability of the software at unprecedented scales. Further implications of the coherent and sliceable mesh representation arise due to simplifications in partitioning and diminished pre- and post-processing overheads.Item Open Access Editorial - visualizing big culture and history data(2025) Windhager, Florian; Koch, Steffen; Münster, Sander; Mayr, EvaItem Open Access Feature-based deformation for flow visualization(2024) Straub, Alexander; Sadlo, Filip; Ertl, ThomasWe present an approach that supports the analysis of flow dynamics in the neighborhood of curved line-type features, such as vortex core lines, attachment lines, and trajectories. We achieve this with continuous deformation to the flow field to straighten such features. This provides “deformed frames of reference”, within which qualitative flow dynamics are better observable with respect to the feature. Our approach operates at interactive rates on graphics hardware, and supports exploration of large and complex datasets by continuously navigating the additional degree of freedom of deformation. We demonstrate the properties and the utility of our approach using synthetic and simulated flow fields, with a focus on the application to vortex core lines.