06 Fakultät Luft- und Raumfahrttechnik und Geodäsie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7
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Item Open Access Water level monitoring at SAPOS stations through GNSS-IR : a case study at the station Iffezheim(2023) Wagner, Sven B.The German SAPOS-Network comprises approximately 270 permanent GNSS receivers, capturing signals from Global Navigation Satellite Systems such as GPS, GLONASS, Galileo, and BeiDou. Primarily employed for generating kinematic, mathematical, and physical models within their respective regions, these receivers hold untapped potential for alternative applications. GNSS receivers capture multipath errors, typically considered unwanted interferences resulting from signal reflections off surfaces beneath the antenna. Despite their potential to adversely affect data precision, these interferences contain valuable information about the reflecting surface. As satellites pass through the receivers’ field of view at specific elevation angles, the interference between the direct and reflected signals leads to constructive and destructive patterns. This phenomenon occurs due to variations in signal phase between the direct and reflected signal, enhancing or dampening the signal strength. These variations in signal strength are captured in the satellites Signal-to-Noise Ratio (SNR) data. Spectral analysis of the SNR data can be used to determine the frequency of the interference pattern. Combining this frequency with the corresponding signal wavelength and satellite elevation angles allows the calculation of the vertical distance between the antenna phase centre and the reflecting surface on Earth. This method, known as GNSS Interferometric Reflectometry (GNSS-IR), provides a valuable means of monitoring surface information, including soil moisture, snow depth, and water levels. At SAPOS stations near rivers and water bodies, GNSS-IR offers a cost-effective, accessible, and innovative opportunity to gather water level information using the already existing infrastructure. This research explores the potential of GNSSIR for water level monitoring at SAPOS stations focusing on the Iffezheim station along the Rhine River near the City of Karlsruhe in southern Germany.Item Open Access Analysis of river surface slope using ICESat-2 satellite altimetry(2022) Bao, JingyiItem Open Access Create a fluid-structure simulation framework for cycloidal rotors(2021) Schließus, JulianThe deformation of cyclorotor blades caused by aerodynamic forces and its effect on the rotor efficiency is not well understood. Therefore the aim of this thesis is to set up coupled Fluid Structure Interaction (FSI) simulations of cycloidal rotors. Furthermore, the results of this work shall create a base for prospective refinements of current cyclorotor CFD models in using a coupled simulation. For the FSI setup, the Computational Fluid Dynamics (CFD) simulation software OpenFOAM and the Multibody Dynamics (MBD) simulation software MBDyn are coupled using the coupling library preCICE. During this thesis, MBDyn models are set up and the advantages and limits of the currently existing preCICE OpenFOAM- and MBDyn-Adapter are discussed. To extend the coupling possibilities into the territory of rotating bodies, the creation of a custom OpenFOAM class is explained in this work. In addition, the influence of the cell displacement tolerance on mesh deformation is investigated and issues in OpenFOAM such as unwanted scaling or nonphysical motions are solved. Further, 2D and 3D setup cases are run and tested successfully on a High Performance Computing (HPC) cluster. Finally, certain coupling methods are reviewed and evaluated for the considered case.Item Open Access Spacecraft data simulator for the DESTINY⁺ Dust Analyser(2021) Kniese, RafaelThis bachelor thesis reports on the development of a data simulator for the dust telescope "DESTINY⁺ Dust Analyser (DDA)". The DDA is part of DESTINY⁺, a space mission to the asteroid 3200 Phaethon, the presumed parent body of the Geminids. It will analyze cosmic dust released by the asteroid to better understand its role as a source of organic material on earth. The DDA will communicate with the rest of the satellite using the SpaceWire bus system and will be tested by the data simulator developed in this thesis, so that possible errors in the flight software can be detected and corrected as soon as possible. The need for this arises from the fact that the DDA is being realized at the Institute of Space Systems of the University of Stuttgart (IRS) together with the electronics supplier "von Hoerner & Sulger", while DESTINY⁺ is a mission of the Japan Aerospace Exploration Agency (JAXA). The German Aerospace Center (DLR) is the German project sponsor. The geographical distance between the experiment and the spacecraft is too large to perform direct tests in the early stages of the mission. The data simulator is implemented as two Graphical User Interfaces (GUIs) in C/ C++ in the Microsoft Visual Studio 2019 environment on Microsoft Windows 10. One sends data as broadcast or telecommand, the other receives telemetry. A SpaceWire Brick Mk3 from STAR-Dundee is used as the interface between the PC and the bus, which has two ports for SpaceWire cables and a USB port. Thus the data stream from and to the DDA can be controlled from a PC. The messages follow the packet protocol of the Consultative Committee for Space Data Systems (CCSDS). In the future, however, they will be adapted to the Remote Memory Access Protocol (RMAP).Item Open Access Optimizing automated postprocessing of point clouds for accurate wind turbine blade CFD analysis(2024) Schollenberger, KaiItem Open Access Dealing with challenges of altimetry-based surface water height derivation over boreal catchments : case study of Mackenzie river(2022) Liu, JiaxinThe Earth is a watery place, which fills the oceans, rivers, and lakes. Approximately 71% of the Earth’s surface is water-covered. Measurements of surface water level in oceans, lakes, rivers and coastal waters are important for a variety of reasons. In the short term, this can, for example, help to alert to dangerous water level so that actions can be taken in advance, while in the long term, monitoring water levels can provide even greater insight into patterns of water dispersal in the area, and measure, for example, the effects of global warming. Satellite altimetry, which was originally designed for oceanography in the 1970s, has revolutionized our knowledge of the marine gravity field, of the dynamics of the oceans and even ofland hydrology. It is a space measurement technique that uses artificial satellites to measure the altitude from the satellite to the Earth’s surface. Due to its high resolution, global coverage and short revisit time, it is playing an increasingly important role in measurements of water level. For some years, this technology has also been used to retrieve water levels from rivers, lakes, and any inland water body as well. However, compared with the wide seas, measurements of inland water bodies involve many challenges. In this paper, we will take the Mackenzie River in northern Canada as a research object and process the data through the Matlab-based program Atlbundle+ to study the potential of inland altimetry, the problems it faces and the possible ways to find the solution. In general, there are two perspectives that will be considered: Firstly, how we can accurately remove outliers in the measurements, and secondly, how to improve the altimetry-driven water level time series by improving the retracking methods. Finally, based on the results and the procedure, a systematic analysis of the inland altimetry can be carried out.Item Open Access Konstellationsentwürfe und Bewertungen einer VLEO Schwerefeldmission(2024) Edelmann, ChristianItem Open Access Experimental validation of a cycloidal rotor URANS CFD model and geometric parameter optimization(2022) Donners, LeonardCycloidal rotors offer many properties that are beneficial to VTOL rotor concepts. Two examples are high manoeuvrability and low aerodynamic noise emission. These rotors use cyclically pitched axial blades to generate thrust and operate in highly unsteady flow regimes, including curvilinear flow and dynamic stall phenomena. The current work develops an unsteady, incompressible 3D URANS CFD simulation setup that models a given small-scale experimental rotor. Measurements and simulation are conducted at a relatively low and slim Reynolds number range of 12x10^3 ≤ Re ≤ 76x10^3. By comparison of simulation results and experimental data, the CFD setup is validated. The validated setup is used to investigate flow phenomena on the initial rotor configuration and further conduct multiple separate parametric studies to optimise the rotor's energy efficiency. The investigated parameters are the blades' pitch profile, the number of blades, blade span and the addition of endplates at the blade tips. The highest efficiency increase of 14% compared to the experimental rotor is hereby found when adding endplates. The most efficient pitch profile results with a pitch rod length of l_opt=87 mm. The optimal blade span aspect ratio is 6 and a four-blade rotor is most efficient. Further research may aim at conducting this optimisation in a wider Reynolds number range or finding an optimum of multiple variable parameters combined.Item Open Access Investigation of the Reynolds Number on the performance of a cycloidal rotor(2021) Zimmer, FlorianThe Reynolds number has great influence on the provided lift and requested power of a cycloidal rotor. The aim of the present paper is to determine lift, power and efficiencyof a three bladed cycloidal rotor in relation to the Reynolds number. The investigated range of Reynolds numbers reaches from Re=10x10^3 to Re=600x10^3. For the parameter study, a cycloidal rotor under stationary hovering conditions, using a instationary, incompressible 2D URANS CFD simulation has been investigated. To interpret the rotation averaged data, field solutions are provided. Two different flow regimes can be distinguished: For the first regime (10x10^3≤Re≤100x10^3), two dynamic flow detachments occur, the first one at a maximum pitch angle of Ψ=270° and the second shortly afterwards. The second flow regime (200x10^3≤Re≤600x10^3) avoids the first detachment due to the increased Reynolds number. Both detachments are perceptible in the flow field solution as well as in the azimuthal lift distribution. The rotation averaged lift and power follow the proportionalities obtained by momentum theory.Item Open Access Create an automated structured mesh generation method for rotor blades using exclusively open source software(2023) Heider, Michael AndreasThe generation of high-quality CFD meshed wings for wind energy turbines currently requires either a very laborious process of building each wing by hand or requires the purchase of very expensive software. With university budgets and the advantages of open-source in mind, an open-source solution is desirable. The following thesis tackles this problem via a grid generation code in Python with Gmsh and extrusion via Pyhyp. However, designing software that has all of the features of commercial software with open source software leads to situations in which the intended way of usage is not the best way for the given task. An example of another open-source approach is the MACH-AERO framework which is an aerodynamic shape optimization tool that creates a grid along the way and extrudes it. However, this does not cover the intended usage of openblademesh for purely structured grid generation for predefined wings. Here we show one way to achieve an open-source solution with Gmsh and Pyhyp. All the necessary software, the versions needed, and installation instructions are described. Also how the wing generation process is achieved with special concentration on the wing-tip is part of the following thesis. The thesis also describes how to use the presented software Openblademesh and how to achieve the best results. The tool uses various automatisms to take the workload off of the user and helps to achieve the best mesh. Finally, the advantages and limitations of the tool are assessed and future extensions are described.