ВЛИЯНИЕ ТРАНСПОРТНыХ ЗАДЕРЖЕК ШЛАМОВыХ ПОТОКОВ НА ПРОДОЛЖИТЕЛЬНОСТЬ НЕСТАЦИОНАРНОГО РЕЖИМА РАБОТы ВОДНО-ШЛАМОВыХ СИСТЕМ

Проблема и ее связь с научными и практическими задачами. Все подре-шетные воды гравитационного отделения аккумулируются в зумпфах большой емкости и далее перекачиваются на операцию предварительной регенерации в гидроциклоны, классификаторы или сгустители. При этом необходимо обеспе-чить подачу на самую верхнюю отметку для дальнейшего распределения шла-мовых потоков самотеком. Как правило, такие потоки характеризуются высо-кими транспортными задержками. Магистрали для шламовых потоков перед узлами вывода имеют меньшие геометрические размеры, переносят незначи-тельное количество пульпы по сравнению с вводными коммуникациями

Development and investigation of a particle method for the simulation of electromagnetic interactions in rarefied plasma flows

In einer Vielzahl von technischen Prozessen und Geräten, insbesondere in der Raumfahrt, spielen verdünnte Plasmaströmungen eine signifikante Rolle. Zur Erforschung, Auslegung und Optimierung dieser Prozesse und Geräte können numerische Plasmasimulationen einen wertvollen Beitrag liefern. Aufgrund der dünnen Plasmen und der damit verbundenen Ungültigkeit der Kontinuumsannahme werden Partikelverfahren verwendet. Gekoppelte PIC-DSMC-Verfahren zur Approximation der Boltzmanngleichung können sowohl elektromagnetische Interaktionen als auch Kollisionen der Partikel behandeln. Ein solches Verfahren wird derzeit in einer Kooperation zwischen dem Institut für Raumfahrtsysteme (IRS) und dem Institut für Aerodynamik und Gasdynamik (IAG) der Universität Stuttgart entwickelt, mit früheren Beteiligungen des Karlsruher Institut für Technologie (KIT), des Höchstleistungsrechenzentrums Stuttgart (HLRS) und der German Research School der RWTH Aachen. Die vorliegende Arbeit befasst sich mit der Entwicklung und Untersuchung von Teilen der PIC-Komponente dieses gekoppelten PIC-DSMC-Verfahrens und stellt die implementierten Verfahren und Techniken sowie die durch die Verifizierung und Untersuchung gewonnenen Erkenntnisse vor. Die theoretischen Grundlagen und physikalischen Zusammenhänge sowie die grundlegenden Gleichungen werden vorgestellt. Die Modellierung und Implementierung des PIC-Verfahrens wird erläutert und die räumlichen und zeitlichen Diskretisierungsmethoden sowie Randbedingungen des Verfahrens werden präsentiert. Der Fokus der Arbeit liegt auf der Partikelbehandlung. Dazu gehören unter anderem die Partikellokalisierung und -verfolgung bezüglich des Rechengitters sowie die Randbehandlung der Partikel. Die entwickelten und vorgestellten Methoden ermöglichen eine zuverlässige und schnelle Verfolgung der Partikel auf unstrukturierten Gittern mit nicht planaren Flächen zwischen Gitterelementen. Dadurch wird allgemein die sichere Anwendung von Randbedingungen, für das PIC-Verfahren die korrekte Zuordnung der Partikel zu den Rechengitterelementen und für das DSMC-Verfahren die schnelle Erfassung der in einem Element befindlichen Partikel gewährleistet. Ein weiterer Aspekt der Partikelbehandlung ist die Deposition der Ladungen von den Partikeln auf das Rechengitter selbst, für die verschiedene Methoden präsentiert werden. Durch eine grundlegende Untersuchung dieser Methoden hinsichtlich Rechenaufwand, Ladungserhaltung und -verteilung wird deren Eignung für verschiedene Anwendungsbereiche und deren spezifischen Anforderungen identifiziert. Für die bisher verwendete Formfunktionsmethode wurde eine Alternative hoher Ordnung auf der Basis von B-Splines eingeführt, die durch die Verwendung eines kartesischen Hintergrundgitters zur Deposition zu einer signifikanten Reduzierung des Rechenaufwands führt. Da die Simulation der meisten Anwendungsfälle aufgrund der Notwendigkeit von hohen Partikelzahlen und hochaufgelösten Rechengittern sehr rechenintensiv ist und somit die Verwendung von parallelen Hochleistungsrechnern erfordert, ist das Verfahren voll parallelisiert. Die Methoden zurParallelisierung der einzelnen Teile des Verfahrens werden vorgestellt. Darüber hinaus wird die Skalierbarkeit und die Verteilung der Rechenlast gezeigt. Das PIC-Verfahren wird verifiziert und die Anwendbarkeit des Verfahrens am Beispiel der Simulation einer Strömung durch das Gitter eines Ionentriebwerks demonstriert. Die in dieser Arbeit vorgestellten Verfahren und Techniken ermöglichen die parallele Simulation von dreidimensionalen verdünnten Plasmaströmungen auf komplexen Geometrien unter Verwendung des Discontinuous Galerkin Verfahrens hoher Ordnung, wofür die hierfür entwickelten und untersuchten Partikelbehandlungsmethoden einen wesentlichen Beitrag leisten.For many technical processes and devices, especially for space applications, rarefied plasma flows play a significant role for their working principle. Plasma simulations can be a valuable contribution to the research, design and optimization of these processes and devices. Due to the rarefied character of the plasma flows, they cannot be treated as continuum flows, instead particle methods are applied. Coupled PIC-DSMC methods for the approximate solution of the Boltzmann equation allow the simulation of electromagnetic interactions as well as particle collisions. Such a method is currently developed in cooperation between the Institute of Space Systems (IRS) and the Institute of Aerodynamics and Gasdynamics (IAG) of the University of Stuttgart, with previous participation by the Karlsruhe Institute of Technology (KIT), the High Performance Computing Center Stuttgart (HLRS) and the German Research School of the RWTH Aachen. The topic of this work is the development and investigation of the PIC part of the coupled method and it presents the implemented methods and techniques as well as the results and insights gained by the verification and investigation. The theoretical and physical foundations and the basic equations are outlined. The modeling and implementation of the PIC method are discussed and the spatial and temporal discretization methods as well as the boundary conditions are presented. This work focuses on the particle treatment. This includes particle localization, particle tracking and the boundary treatment of particles with respect to the computational grid. The developed and presented methods allow reliable and fast tracking of the particles on unstructured grids with non-planar volume element boundaries. Thereby, the accurate application of particle boundary conditions and the correct mapping of particles to the computational grid as well as the fast compilation of particles within a grid element is ensured, the latter being of high importance for the DSMC method. An additional aspect of the particle treatment is the deposition of the particle charges onto the computational grid, for which several methods are presented. An extensive investigation of these deposition methods with regard to computational cost, charge conservation and charge distribution is conducted and their suitability for different areas of application is identified. A B-splines based alternative to the commonly used method of employing high order shape functions is introduced and applied to the deposition via a Cartesian background mesh, which significantly reduces computational costs. For most applications, large numbers of particles and high resolution grids must be employed, requiring high computational effort. Therefore, to facilitate high performance computing, the method has been fully parallelized and the parallelization methods in use for the different parts of the PIC code are presented within this work. Additionally, scalability tests and profiling of the code are performed and the results are shown. A verification of the PIC code is conducted and the application of the code is demonstrated using the example of a simulation of the plasma flow through the grid of an ion thruster.The methods and techniques presented in this work enable the parallel simulation of three dimensional rarefied plasma flows with complex geometries via the high order discontinuous Galerkin method, for which the particle treatment methods developed and investigated in this work provide a substantial contribution

The Digital Concurrent Engineering Platform DCEP

In the field of aerospace applications, a wide spread of highly specialized domains exists, with dataand expertise being distributed among different institutes and companies due to product complexity anddiversity. Providing easy and secure access to shared and individual resources during product developmentis a significant challenge. Additionally, the necessity of exchanging design documents and specificationsas well as data in different formats contributes to development costs and time. Digital platforms canprovide a solution for these issues by allowing different institutions and experts to securely and remotelyshare their tools and knowledge and by providing a common data base during development.The Institute of Structures and Design of the German Aerospace Center (DLR) is currently developingthe Digital Concurrent Engineering Platform (DCEP) in the project IRAS (Integrated Research platformfor Affordable Satellites) to enable cooperative, distributed development of satellites. The DCEP providesa web-based software platform for model-based engineering in the form of a parametrical representation ofthe design tree. Concepts and technologies to allow faithful collaboration between potentially competingcompanies are developed and adopted. This includes indirect access to connected software tools anddatabases as well as secure traceability of modifications and contribution authorship. The current focusof the DCEP platform are the early design phases, with support for automated design tools and algorithmsdeveloped within IRAS. Long-term goal of DCEP development is the creation of a platform that managesdigital data and collaborative development through all phases of a satellite life cycle, from early designto production and operation up to decommissioning. For this, the DCEP platform design is based on adistributed, modular concept, which enables future extensions and additionally provides opportunities forthe DCEP to be used for a wide range of other potential applications outside of satellite development.This paper will provide an overview of the platform’s concepts, methods and technologies and presentthe current state of development as well as planned future steps

IRAS II Abschlussbericht

Dieser interne Bericht enthält die Aktivitäten des IRAS II-Projekts aller Partner, die vom Projektbeginn am 1.12.2018 bis zum Projektende am 31.5.2020 stattfanden

IRAS III Abschlussbericht

Dieser interne Bericht enthält die Aktivitäten des IRAS III-Projekts aller Partner, die vom Projektbeginn am 01.01.2020 bis zum Projektende am 20.06.2022 stattfanden

Application of Automated Design Tools for Satellite Missions with the Design Platform DCEP

Within the project IRAS (Integrated Research Platform for Affordable Satellites), digital tools for the fast and semi-automated early design of space missions are being developed. The constellation design tool TOCASTA (Tool for Constellation and Satellite Trade-off Analysis) identifies possible satellite constellation solutions based on coverage requirements using a semi-analytical method. It uses the commercial simulation software ASTOS to refine solutions for optimized constellation design, and performs an automated mission analysis for each solution, aided by the ESA-DRAMA software. The satellite design tool ESDC (Evolutionary System Design Converger) accelerates spacecraft design using heuristic scaling laws and evolutionary algorithms. These laws, in combination with user-defined requirements, generate estimates for subsystems, while parametric models and component-based dimensioning further predict detailed spacecraft designs. Evolutionary algorithms optimize each configuration to minimize the overall system mass. The Digital Concurrent Engineering Platform DCEP offers a web-based service for cooperative model-based systems engineering, and acts as platform for the software-aided design process by providing an intuitive user interface. It contains a parametric representation of the satellite and manages data transfer and integration of other IRAS- and third-party tools. The tools are coupled to the DCEP via an SSH-based method that allows data linking and management of the tools as well as accessing their results via the DCEP user interface, with minimal effort for the tool providers. As a first test of the coupled system of tools and DCEP, an exemplary satellite mission design has been conducted. The tools were utilized successfully via the DCEP to design several satellite constellations with different coverage requirements and altitudes. Mass and power budgets as well as thruster recommendations for the individual satellites were established for the different constellation solutions. The coupling of DCEP and tools allowed a seamless transfer of TOCASTA output data to the ESDC, enabling the rapid computation and evaluation of a large number of designs. Potential improvements in user experience and beneficial additional features were identified

IRAS -New technologies for low cost satellites

To persist in the space business low cost satellites with a short production time and life-spans of 1-4 years are the way to go. In the Integrated Digital Research Platform for Affordable Satellites (IRAS) project we work towards making affordable technologies fit for space. Off-the-shelf components e. g. from automotive industry are researched andadapted to make them usable in space. To achieve this, additive manufacturing techniques using polymeric, metallic, and ceramic materials are combined with multifunctional and bionic structures, resulting in lightweight, cost-efficient and integrated structures. Satellite propulsion is also considered and two green propulsion systems are being developed.Furthermore, a Digital Concurrent Engineering Platform (DCEP) is under development. This platform will enable engineers to jointly develop satellites in anew way without the need of physical proximity.This paper presents the concepts and current developments in these fields and details how new technologies can be combined to develop multifunctional structures such as the integration shielding against cosmic raysdirectly into additively manufactured satellite structures. These new developments are integrated in the technology demonstrator satellite missions SOURCE, a CubeSat, and a microsat OREUS

Abschlussbericht IRAS

Abschlussbericht zum Projekt IRAS vom 1.12.2016 bis zum 30.6.201