A5103160636- Fluid Dynamics and Turbulent Flows
- Particle accelerators and beam dynamics
- Aerodynamics and Acoustics in Jet Flows
- Plasma and Flow Control in Aerodynamics
- Computational Fluid Dynamics and Aerodynamics
- Magnetic confinement fusion research
- Heat Transfer Mechanisms
- Wind and Air Flow Studies
- Particle Accelerators and Free-Electron Lasers
- Fluid Dynamics and Vibration Analysis
- Gyrotron and Vacuum Electronics Research
- Acoustic Wave Phenomena Research
- Aeroelasticity and Vibration Control
- Aerodynamics and Fluid Dynamics Research
- Computer Graphics and Visualization Techniques
- Adaptive optics and wavefront sensing
- Slime Mold and Myxomycetes Research
- Laser-Plasma Interactions and Diagnostics
- Material Properties and Processing
- X-ray Spectroscopy and Fluorescence Analysis
- Linguistic research and analysis
- Advanced Control Systems Optimization
- Muon and positron interactions and applications
- Planetary Science and Exploration
- Physics of Superconductivity and Magnetism
Helmholtz-Zentrum Berlin für Materialien und Energie
2020-2024
Institut für Sonnenphysik
2020
Folkwang University of the Arts
2020
University of Siegen
2020
Technische Universität Berlin
2008-2017
Technische Universität Dresden
2006
Leibniz Institute for Astrophysics Potsdam
2004
The GREGOR telescope was inaugurated in 2012. In 2018, we started a complete upgrade, involving optics, alignment, instrumentation, mechanical upgrades for vibration reduction, updated control systems, and building enhancements and, addition, adapted management policies. This paper describes all major updates performed during this time. Since 2012, powered mirrors except M1 were exchanged. Starting from 2020, observes with diffraction-limited performance new optics instrument layout.
X-ray fluorescence (XRF) analysis is one of the standard tools for stratified materials and widely applied investigation electronics coatings. The composition thickness layers can be determined quantitatively non-destructively. Recent work showed that these capabilities extended towards retrieving stratigraphic information like concentration depth profiles using angle-resolved XRF (ARXRF). This paper introduces an experimental sample chamber which was developed as a multi-purpose tool...
A combined numerical and experimental study is carried out to investigate the capability of sinusoidal riblet patterns reduce turbulent drag. In contrast conventional straight riblets, riblets are able induce a small amount lateral motion in ow. Therefore, they thought emulate eect wall oscillations hence achieve higher reduction drag than riblets. This parameter shows that velocity successfully induced. Positive eects geometric amplitudes weak could not be determined outside uncertainty...
This paper presents the optimal design of an active flow control mechanism for industry relevant complex high-lift configuration. To flow, a large number synthetic jet actuators are placed on wing and flap faces. The actuation parameters at these faces considered as variables. set that yield maximum mean-lift is evaluated by combining unsteady discrete adjoint RANS solver with gradient based optimisation algorithm. developed employing Algorithmic Differentiation (AD) techniques. Numerical...
A novel approach using laterally oscillating riblets is investigated to reduce the turbulent drag of wall-bounded flows. The new method intended combine eect wellknown stationary with strong lateral wall-oscillations. Experimental investigations in this study show only minor eects for parameters investigated. DNS results demonstrate that secondary flow induced by riblet motion has a influence on amount reduction. not straightforward since stronger oscillations can lead higher under certain...
This paper presents the development of an accurate and robust discrete adjoint approach for optimization active flow control mechanism. The solver is developed by applying algorithmic differentiation techniques to incompressible unsteady Reynolds-averaged Navier–Stokes solver. Coupled with a quasi-Newton gradient-search algorithm, its applicability demonstrated finding optimal synthetic jet actuation on suction side NACA 4412 airfoil at Reynolds number angle incidence 20 deg. Numerical...
Abstract A first series of nitrogen infusion runs 1.3 GHz single-cell cavities at DESY resulted in an unexpected and severe deterioration observed during the vertical cold test. To investigate origin deterioration, one underwent extensive radio-frequency measurements a temperature- magnetic field-mapping was performed collaboration with Helmholtz-Zentrum Berlin. After combining all results, regions interests were identified cut-out cavity. Subsequent surface analysis techniques (EBSD, PALS,...
Active flow control techniques are used to delay or prevent the turbulent separation on flap of a high-lift configuration. Effective and thus lift enhancement can be achieved by finding optimal set actuation parameters, which may in very large number. In this paper, consistent unsteady discrete adjoint RANS solver three-dimensions is developed towards objective parameters. The code applied sensitivity analysis practically relevant three-dimensional sensitivities with respect parameters based...
Further development and validation of an innovative DES-based methodology for the prediction jet noise from installed configurations is presented. A Grey-Area improved Delayed Detached-Eddy Simulation (DDES) model has been implemented in industrial solver validated a static single-stream jet. The measured far-field sound directivity was predicted to within 2 dB frequencies up around St = 3 were resolved on grid 15.4M cells. To address key problem defining suitable location data surface...
In order to minimize the surface resistance in superconducting cavities, a deeper understanding of residual due trapped magnetic flux is necessary. For that purpose, combined temperature and field mapping system employed map cavity, related increase resistance. By cooling down 1.3 GHz TESLA single cell cavity several times with externally applied static fields different orientations respect statement can be made about how angle between cavity's affects trapping, example, significantly higher...
Although there seems to be agreement that the SnAgCu-solder is lead-free alloy of choice, basic eutectic SnAgCu system does not fully satisfy requirements an alternative classic SnPb system. Therefore question is, how simple needs changed in order achieve a higher mechanical performance solder. Changes include increase or reduction Sn-, Ag- Cu-content non solder, addition other alloying elements like Ni, Au and Co. The scope paper present creep data, was gained on specimens with different...
We present the final opto-mechanical design of Large Binocular Telescope (LBT) Acquisition, Guiding and Wavefront Sensing Units (AGW-units) together with laboratory test performance units. The units will be installed at LBT shortly after this conference, several different Gregorian focal positions available. Each AGW-unit consists a probe camera wavefront sensor located in front science instrument. can move two axes allowing it to patrol field off-axis field. A dichroic beam-splitter on...
Blade-shaped riblets are tilted sinusoidally at specific frequencies to reduce turbulent friction drag. Within this investigation, the overall drag reduction of stationary could be improved by oscillation from 8.6% 11.1%. Two examplary cases presented, one showing an increase in and with only minor changes compared riblets. Detailed analysis data direct numerical simulations reveals that additional is mostly related a smaller contribution riblet tips which caused secondary motion low-speed...
Many modern accelerators rely on superconducting radio-frequency (SRF) cavities to accelerate particles. When these are cooled the state, a fraction of ambient magnetic field (e.g., Earth’s field) may be trapped in superconductor. This flux can significantly increase power dissipation SRF cavities. It is, therefore, crucial understand underlying mechanism how is and what treatments operating conditions reduce flux-trapping efficiency. A new experiment was designed that enables systemic...