Adjoint-Based Error Estimation and Mesh Adaptation for Hybridized Discontinuous Galerkin Methods

We present a robust and efficient target-based mesh adaptation methodology, building on hybridized discontinuous Galerkin schemes for (nonlinear) convection-diffusion problems, including the compressible Euler and Navier-Stokes equations. Hybridization of finite element discretizations has the main advantage, that the resulting set of algebraic equations has globally coupled degrees of freedom only on the skeleton of the computational mesh. Consequently, solving for these degrees of freedom involves the solution of a potentially much smaller system. This not only reduces storage requirements, but also allows for a faster solution with iterative solvers. The mesh adaptation is driven by an error estimate obtained via a discrete adjoint approach. Furthermore, the computed target functional can be corrected with this error estimate to obtain an even more accurate value. The aim of this paper is twofold: Firstly, to show the superiority of adjoint-based mesh adaptation over uniform and residual-based mesh refinement, and secondly to investigate the efficiency of the global error estimate

A Comparison of Hybridized and Standard DG Methods for Target-Based hp-Adaptive Simulation of Compressible Flow

We present a comparison between hybridized and non-hybridized discontinuous Galerkin methods in the context of target-based hp-adaptation for compressible flow problems. The aim is to provide a critical assessment of the computational efficiency of hybridized DG methods. Hybridization of finite element discretizations has the main advantage, that the resulting set of algebraic equations has globally coupled degrees of freedom only on the skeleton of the computational mesh. Consequently, solving for these degrees of freedom involves the solution of a potentially much smaller system. This not only reduces storage requirements, but also allows for a faster solution with iterative solvers. Using a discrete-adjoint approach, sensitivities with respect to output functionals are computed to drive the adaptation. From the error distribution given by the adjoint-based error estimator, h- or p-refinement is chosen based on the smoothness of the solution which can be quantified by properly-chosen smoothness indicators. Numerical results are shown for subsonic, transonic, and supersonic flow around the NACA0012 airfoil. hp-adaptation proves to be superior to pure h-adaptation if discontinuous or singular flow features are involved. In all cases, a higher polynomial degree turns out to be beneficial. We show that for polynomial degree of approximation p=2 and higher, and for a broad range of test cases, HDG performs better than DG in terms of runtime and memory requirements

NRW80+ Hochaltrigenstudie: Abschlussbericht zur ersten Förderphase 01/2016-12/2018

Der Abschlussbericht beschreibt die Ausgangslage, Vorarbeiten, Durchführung, erste Ergebnisse und Implikationen der Studie "Lebensqualität und Wohlbefinden hochaltriger Menschen in NRW" (NRW80+). Ziel der Studie war es, die Lebenssituation und Lebensqualität hochaltriger Menschen in Nordrhein-Westfalen umfassend zu untersuchen. Im Rahmen einer repräsentativen Querschnittsbefragung wurden Personen ab 80 Jahren befragt, wobei auch gesundheitlich beeinträchtigte (u.a. über Stellvertreter:innen-Interviews) und in Heimen lebende Hochaltrige explizit eingeschlossen wurden. Die erhobenen Daten schließen diverse Aspekte der objektiven Lebens- und Ressourcenlagen sowie der subjektiven Bewertungen und gesellschaftlichen Wertvorstellungen ein. In diesem Bericht werden die ersten deskriptiven Ergebnisse zu Themen wie allgemeine Lebenszufriedenheit, Depressivität, subjektive Gesundheit, Pflegebedürftigkeit und Pflegenutzung, soziale Netzwerke, Anomie und Internetnutzung dargestellt. Darüber hinaus wird auf Basis von beispielhaften multivariaten Analysen beschrieben, wie die Verfügbarkeit von Lebensqualitätsresourcen (z.B. Gesundheit, Freizeitgestaltung) zur Erklärung von Ungleichheiten in Lebensqualitätsoutcomes (z.B. Lebenszufriedenheit, Wertschätzung) beiträgt. Neben den Ergebnissen der quantitativen Erhebung werden auch Befunde aus den teilstandardisierten leitfadengestützten Interviews mit Stakeholdern vorgestellt, die aus gesellschaftlich relevanten Handlungs- und Entscheidungsfeldern stammen

UNICARagil – New architectures for disruptive vehicle concepts

This paper provides an overview of the research topics of the UNICARagil project with the focus on different architectures, such as the mechatronic, the software, and the mechanic architecture. The main research questions as well as possible solutions, which will be investigated in this project, are described. The project is funded by the Federal Ministry of Education and Research of Germany In terms of the mechatronic and the software architecture, this paper focuses on the ECU concept: the main tasks of the automated driving process are executed on three ECUs, which are called the cerebrum, the brainstem and the spinal cord. This architecture supports the modular approach regarding functional safety, the ability of future updates and upgrades, and the service orientated architecture (SOA) of the software. The well-known SOA approach is transferred to automotive applications and becomes the automotive service orientated architecture (ASOA). Furthermore, the mechanic structure of the four vehicles AUTOtaxi, AUTOelfe, AUTOliefer and AUTOshuttle is described

UNICARagil - Disruptive Modular Architectures for Agile, Automated Vehicle Concepts

This paper introduces UNICARagil, a collaborative project carried out by a consortium of seven German universities and six industrial partners, with funding provided by the Federal Ministry of Education and Research of Germany. In the scope of this project, disruptive modular structures for agile, automated vehicle concepts are researched and developed. Four prototype vehicles of different characteristics based on the same modular platform are going to be build up over a period of four years. The four fully automated and driverless vehicles demonstrate disruptive architectures in hardware and software, as well as disruptive concepts in safety, security, verification and validation. This paper outlines the most important research questions underlying the project

Automation of the UNICARagil Vehicles

The German research project UNICARagil is a collaboration between eight universities and six industrial partners funded by the Federal Ministry of Education and Research. It aims to develop innovative modular architectures and methods for new agile, automated vehicle concepts. This paper summarizes the automation approach of the driverless vehicle concept and its modular realization within the four demonstration vehicles to be built by the consortium. On-board each vehicle, this comprises sensor modules for environment perception and modelling, motion planning for normal driving and safe halts, as well as the respective control algorithms and base functionalities like precise localization. A control room and cloud functionalities provide off-board support to the vehicles, which are additionally addressed in this paper

Reduction of Film Coolant in High Pressure Turbines

Gas turbine development has been in the direction of increased turbine inlet temperatures to improve efficiency and power output. As a result the allowable metal temperatures of the alloys used for the turbine airfoils and endwalls are exceeded such that the surfaces have to be protected from the hot gases by cooling. Bypassed leakage flows emerging from a slot between the combustor and turbine component endwalls can be utilized for cooling purposes. In order to improve this cooling method the complex flow structures in a turbine have to be considered as they enhance the heat transfer and convect hot core flow gases onto component surfaces. In this thesis four film cooling configurations using this slot which differ from each other in terms of geometrical aspects are examined with the help of the flow solver TRACE (Turbomachinery Research Aerodynamics Computational Environment) developed at the Institute of Propulsion Technology of the German Aerospace Center. Furthermore, in the present study the amount of coolant ejected is varied by adjusting the blowing ratio. Additionally the shape of the leakage slot is tailored to take the pressure distribution in front of the leading edge into account. The results are analysed with respect to film cooling effectiveness and the surface heat transfer. The results are mainly influenced by the three-dimensional flow structures visualized with the streamwise vorticity. The results obtained for the straight slot show for all mass flow ratios an intensified ejection of coolant in the center of the passage due to the wall pressure distribution. Furthermore, the coolant is not only concentrated in the center of the passage but also “trapped” between the two legs of the horseshoe vortex, where the coolant air is scraped away from the endwall in the region of the separation lines. With increasing mass flow rate of the coolant one realizes a broader area of the endwall covered by the coolant. By adapting the contour of the slot concerning the pressure distribution in front of the leading edge the coolant is enabled to leave the slot in a much more uniform manner. This way a better cooling around the leading edge region and the juncture of the blade’s pressure side and the endwall is achieved. Thus, not only the need for complex cooling hole layouts next to the critical areas can be minimized but also the number of cooling holes and thus the amount of coolant can be reduced

Reduction of Film Coolant at the Sidewall of the High Pressure Turbine Cascade T6.2

This report documents the results of numerical experiments investigated with the help of the computational fluid dynamics solver TRACE which were performed along the sidewall of a plane turbine cascade considering four film cooling configurations with slot ejection. In doing so, two configurations which have been experimentally examined within two German research projects: AG-Turbo Plattformk¨uhlung I + II are adopted. Furthermore, the effect of a contoured slot taking the pressure distribution at the inlet region of the cascade sidewall into account is studied. The results are analyzed with respect to film cooling effectiveness and the surface heat transfer. The results are mainly influenced by the three-dimensional flow structures visualized with the stream-wise vorticity