TY - CHAP A1 - Neef, Matthias A1 - Hummel, Dietrich T1 - Euler solutions for a finite-span flapping wing T2 - "Fixed, flapping and rotary wing vehicles at very low Reynolds numbers, Notre Dame, Indiana, USA Y1 - 2000 ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, Dietrich ED - Mueller, Thomas J. T1 - Euler Solutions for a Finite-Span Flapping Wing T2 - Fixed and Flapping Wing Aerodynamics for Micro Air Vehicle Applications Y1 - 2001 SN - 978-1-56347-517-7 U6 - https://doi.org/10.2514/5.9781600866654.0429.0451 VL - 16 SP - 429 EP - 451 PB - American Institute of Aeronautics and Astronautics CY - Reston, VA ER - TY - THES A1 - Neef, Matthias T1 - Analyse des Schlagfluges durch numerische Strömungsberechnung N2 - Mit Hilfe eines Finite-Volumen-Verfahrens wird die dreidimensionale reibungsbehaftete Stroemung um einen schlagenden Fluegel berechnet. Die Bewegungsparamter sind dabei vergleichbar mit den Bedingungen im Reiseflug grosser Voegel. Das numerische Verfahren wird fuer den gezeigten Anwendungsfall, indem eine Methode zur Realisierung von beliebigen periodischen Bewegungen implemetiert wird. Eine Verifizierung erfolgt durch den Vergleich mit analytischen, numerischen und experimentellen Ergebnissen aus der Literatur. Mit dem verifizierten Verfahren werden die instationaeren Groessen wie Druck und Geschwindigkeiten in der Umgebung des bewegten Fluegels berechnet. Daraus ergeben sich ferner die zeitlich gemittelten Groessen wie Schub und Wirkungsgrad des Schlagfluges. Ausserdem wird die Interaktion von Laengs- und Querwirbeln im Nachlauf des schlagenden Fluegels untersucht. Es zeigt sich ein dominanter Einfluss der pulsierenden Randwirbel aufgrund der endlichen Spannweite, waehrend die Anfahr- und Stoppwirbel, verursacht durch die Fluegelbewegung, im Reiseflug grosser Voegel nahezu vernachlaessigbar erscheinen. N2 - The three-dimensional viscous flow around a flapping wing is calculated by means of a finite volume code. The invoked motion parameters are comparable with the conditions in cruising flight of large birds. For the described application the numerical procedure is extended by implementing a method for realisation of arbitrary periodic motions. The verification is obtained by comparison with analytical, numerical and experimental results from existing literature. With the verified method the instationary quantities such as pressure and velocity are known in the vicinity of the wing. This also yields the time averaged values such as thrust and propulsive efficiency of the flapping wing propulsion. Additionally, the interaction between longitudinal and transverse vortices in the wake of the flapping wing is investigated. A dominant influence of the oscillating tip vortices due to the finite span can be seen, while the starting and stopping vortices due to the wing motion appear almost negligible in the cruising flight of large birds. Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:084-14501 UR - http://www.digibib.tu-bs.de/?docid=00001361 VL - ZLR-Forschungsbericht, 2 ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, D. ED - Krause, Egon ED - Jäger, Willi T1 - Euler and Navier-Stokes Solutions for Flapping Wing Propulsion T2 - High Performance Computing in Science and Engineering ’01 KW - Wing Motion KW - Computational Fluid Dynamics KW - High Performance Computing KW - Thrust Coefficient Y1 - 2002 SN - 978-3-642-62719-4 U6 - https://doi.org/10.1007/978-3-642-56034-7_37 VL - 30 SP - 386 EP - 395 PB - Springer CY - Berlin ER - TY - CHAP A1 - Jones, Kevin A1 - Castro, Breno A1 - Mahmoud, Osama A1 - Pollard, S. A1 - Platzer, Max A1 - Neef, Matthias A1 - Gonet, K. A1 - Hummel, D. T1 - A collaborative numerical and experimental investigation of flapping-wing propulsion T2 - 40th AIAA Aerospace Sciences Meeting & Exhibit N2 - An international, collaborative investigation is undertaken to evaluate the relative merits and limitations of various numerical methods and experimental measurement techniques, specifically for the analysis of flapping-wing propulsion. A finite aspect-ratio configuration is extensively investigated, both quantitatively and qualitatively, in a low-speed wind tunnel. Direct force measurements are made, as well as time-accurate and time-averaged laser Doppler velocimetry and unsteady flow visualization. The reduced frequency, mean angle of attack, aspect ratio and Reynolds number are varied in the experiments. The experiment is numerically simulated using flatplate theory, two and three-dimensional panel codes, and two and three-dimensional Euler and Navier- Stokes solvers. The ability of each of the methods to capture important aspects of the flow physics are evaluated through comparisons with each other and the experimental data. Additionally, the comparisons indicate areas where further research is needed. The collaborative effort provides a survey of available capabilities and provides a fixed set of flappingwing data for others to compare against. Y1 - 2002 UR - http://arc.aiaa.org/doi/book/10.2514/MASM02 U6 - https://doi.org/10.2514/6.2002-706 PB - American Institute of Aeronautics and Astronautics CY - Reston, Virigina ER - TY - JOUR A1 - Neef, Matthias A1 - Fritzen, J. P. A1 - Schumacher, G. T1 - Evaluation of mount loads in dynamic testing of a jet engine JF - Mechanical Systems and Signal Processing N2 - In the dynamic testing of jet engines the evaluation of loads on the mount structure is vital for comparison with finite element calculations of such testing. Measuring these loads with the help of strain gauges applied to the structure becomes difficult if the mount is overdetermined and thus not every strain gauge can be assigned to a single load direction. In this study, the overdetermined mount structure of the BR715 engine was examined at one of the three mounting points between the Boeing 717 airframe and the engine, where loads in five directions were reacted. Firstly, the dependence of five measured strains upon known static load conditions at the mounting point had to be determined. For this purpose a static calibration test was carried out where defined forces and moments in known directions were applied to the structure while the output from five strain gauges was measured accordingly. The result was the desired relationship between loads and strains in terms of a matrix, which yields the corresponding load condition of the examined mounting point if multiplied with a set of strains. The same calibration procedure was carried out with a finite element model of the mount, where direct comparison to dynamic load results from the model itself was possible. With this model the validity of the above method was shown as well as possible errors which may occur while evaluating dynamic test results. The method was found to give satisfactory results even for dynamic loading, although some inertia forces disturb the signals in dynamic testing. Finally, the results from an actual dynamic engine test were processed into loads and then compared to the simulated loads from a finite element model of the engine. Good agreement was found and the indication of any remaining discrepancies was used to update the model for an even better representation of the dynamic test loads. Y1 - 2003 UR - http://www.sciencedirect.com/science/article/pii/S0888327001914050 U6 - https://doi.org/10.1006/mssp.2001.1405 VL - 17 IS - 3 SP - 665 EP - 681 PB - Elsevier ER - TY - CHAP A1 - Hurd, Paul A1 - Truckenmueller, Frank A1 - Thamm, Norbert A1 - Pollak, Helmut A1 - Neef, Matthias A1 - Deckers, Mathias T1 - Modern Reaction HP/IP Turbine Technology Advances and Experiences T2 - Proceedings of the ASME Power Conference - 2005 : includes papers from the 2005 International Conference on Power Engineering (ICOPE) ; presented at the 2005 ASME Power Conference, April 5 - 7, 2005, Chicago, Illinois, USA Y1 - 2005 UR - https://asmedigitalcollection.asme.org/POWER/proceedings/POWER2005/41820/425/311927 SN - 0-7918-4182-0 U6 - https://doi.org/10.1115/PWR2005-50085 SP - 425 EP - 435 PB - ASME CY - New York ER - TY - CHAP A1 - Völker, Lutz A1 - Casey, Michael A1 - Neef, Matthias A1 - Stüer, Heinrich T1 - The Flow Field and Performance of a Model Low Pressure Steam Turbine T2 - 6th European Conference on Turbomachinery - Fluid Dynamics and Thermodynamics : conference proceedings; 7-11 March 2005, Lille, France N2 - A 3-stage model of a low pressure steam turbine has been equipped with extensive instrumentation to assess aerodynamic performance and for validation of numerical methods. Emphasis was placed on detailed measurements at the inlet and exit of the last stage guide vane. Two configurations were examined – the first used a guide vane with lean in the last stage and a the second used a guide vane combining both lean and sweep. The experimental results from the two configurations have been compared with data from various design methods, ranging from through-flow to 3D multistage viscous simulations with mixing planes. Despite the challenges in modelling complex rotating blades in a wet steam environment, good agreement between the numerical and experimental results was obtained, and the new stator vane combining lean and sweep achieved the desired increase in reaction at the hub section. Y1 - 2005 CY - Lille ER - TY - CHAP A1 - Windte, Jan A1 - Radespiel, Rolf A1 - Neef, Matthias ED - Kroll, Norbert ED - Fassbender, Jens K. T1 - Aerodynamic Analysis of Flapping Airfoil Propulsion at Low Reynolds Numbers T2 - MEGAFLOW - Numerical Flow Simulation for Aircraft Design KW - Lift Curve KW - Chord Length KW - Pitch Motion KW - Laminar Separation Bubble KW - Combine Motion Y1 - 2005 SN - 978-3-540-24383-0 U6 - https://doi.org/10.1007/3-540-32382-1_21 VL - NNFM, 89 SP - 299 EP - 313 PB - Springer-Verlag CY - Berlin, Heidelberg ER - TY - CHAP A1 - Neef, Matthias A1 - Sulda, Erik A1 - Sürken, Norbert A1 - Walkenhorst, Jan T1 - Design Features and Performance Details of Brush Seals for Turbine Applications T2 - Proceedings of the ASME Turbo Expo 2006 : presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain N2 - Adaptive and contacting seals such as brush seals have been successfully applied to turbomachinery for several years. In large steam turbine applications, however, various challenges still persist. Special focus is directed at the long-term performance and longevity of brushes on conventional spring-backed seal segments in steam turbines. This issue is particularly related to wear during startup conditions. This paper discusses the results of wear tests, derived from simulated transient turbine behavior, where the resultant seal leakage under steady state conditions is monitored. It is shown that the brush seal is significantly capable of adapting to varying operating conditions, but exhibits a degree of performance degradation during the initial startups. Together with previously reported mid-term wear data and an experience based long-term phenomenological approach a general model for brush seal performance degradation is developed. This model can be used for performance prediction and exerts influence on brush seal design. Y1 - 2006 SN - 0-7918-4238-X U6 - https://doi.org/10.1115/GT2006-90404 VL - 3 SP - 1385 EP - 1392 PB - ASME CY - New York ER -