TY - JOUR A1 - Zastrow, Udo A1 - Hackl, Klaus T1 - On the existence, uniqueness and completeness of displacements and stress functions in linear elasticity / Hackl, Klaus ; Zastrow, Udo JF - Journal of Elasticity. 19 (1988), H. 1 Y1 - 1988 SN - 1573-2681 SP - 3 EP - 23 ER - TY - JOUR A1 - Götten, Falk A1 - Finger, Felix A1 - Havermann, Marc A1 - Braun, Carsten A1 - Gomez, Francisco A1 - Bill, C. T1 - On the flight performance impact of landing gear drag reduction methods for unmanned air vehicles JF - Deutscher Luft- und Raumfahrtkongress 2018 N2 - The flight performance impact of three different landing gear configurations on a small, fixed-wing UAV is analyzed with a combination of RANS CFD calculations and an incremental flight performance algorithm. A standard fixed landing gear configuration is taken as a baseline, while the influence of retracting the landing gear or applying streamlined fairings is investigated. A retraction leads to a significant parasite drag reduction, while also fairings promise large savings. The increase in lift-to-drag ratio is reduced at high lift coefficients due to the influence of induced drag. All configurations are tested on three different design missions with an incremental flight performance algorithm. A trade-off study is performed using the retracted or faired landing gear's weight increase as a variable. The analysis reveals only small mission performance gains as the aerodynamic improvements are negated by weight penalties. A new workflow for decision-making is presented that allows to estimate if a change in landing gear configuration is beneficial for a small UAV. Y1 - 2018 U6 - https://doi.org/10.25967/480058 PB - DGLR CY - Bonn ER - TY - JOUR A1 - Zastrow, Udo T1 - On the formulation of the fundamental solutions for orthotropic plane elasticity JF - Acta Mechanica. 57 (1985), H. 3-4 Y1 - 1985 SN - 1619-6937 SP - 113 EP - 122 ER - TY - JOUR A1 - Förster, Arnold A1 - Morvic, M. A1 - Betko, J. T1 - On the hopping and band conductivity in molecular-beam epitaxial low-temperature grown GaAs / M. Morvic ; J. Betko ; J. Novák ... A. Förster JF - Physica status solidi / B, Basic research. 205 (1998), H. 1 Y1 - 1998 SN - 1521-3951 SP - 125 EP - 128 ER - TY - JOUR A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - On the influence of elasticity on propeller performance: a parametric study JF - CEAS Aeronautical Journal N2 - The aerodynamic performance of propellers strongly depends on their geometry and, consequently, on aeroelastic deformations. Knowledge of the extent of the impact is crucial for overall aircraft performance. An integrated simulation environment for steady aeroelastic propeller simulations is presented. The simulation environment is applied to determine the impact of elastic deformations on the aerodynamic propeller performance. The aerodynamic module includes a blade element momentum approach to calculate aerodynamic loads. The structural module is based on finite beam elements, according to Timoshenko theory, including moderate deflections. Several fixed-pitch propellers with thin-walled cross sections made of both isotropic and non-isotropic materials are investigated. The essential parameters are varied: diameter, disc loading, sweep, material, rotational, and flight velocity. The relative change of thrust between rigid and elastic blades quantifies the impact of propeller elasticity. Swept propellers of large diameters or low disc loadings can decrease the thrust significantly. High flight velocities and low material stiffness amplify this tendency. Performance calculations without consideration of propeller elasticity can lead to decreased efficiency. To avoid cost- and time-intense redesigns, propeller elasticity should be considered for swept planforms and low disc loadings. KW - Propeller KW - Finite element method KW - Blade element method KW - Propeller elasticity KW - Aeroelasticity Y1 - 2023 U6 - https://doi.org/10.1007/s13272-023-00649-y SN - 1869-5590 (Online) SN - 1869-5582 (Print) N1 - Corresponding author: Felix Möhren VL - 14 SP - 311 EP - 323 PB - Springer Nature CY - Berlin ER - TY - JOUR A1 - Bergmann, Ole A1 - Möhren, Felix A1 - Braun, Carsten A1 - Janser, Frank T1 - On the influence of elasticity on swept propeller noise JF - AIAA SCITECH 2023 Forum N2 - High aerodynamic efficiency requires propellers with high aspect ratios, while propeller sweep potentially reduces noise. Propeller sweep and high aspect ratios increase elasticity and coupling of structural mechanics and aerodynamics, affecting the propeller performance and noise. Therefore, this paper analyzes the influence of elasticity on forward-swept, backward-swept, and unswept propellers in hover conditions. A reduced-order blade element momentum approach is coupled with a one-dimensional Timoshenko beam theory and Farassat's formulation 1A. The results of the aeroelastic simulation are used as input for the aeroacoustic calculation. The analysis shows that elasticity influences noise radiation because thickness and loading noise respond differently to deformations. In the case of the backward-swept propeller, the location of the maximum sound pressure level shifts forward by 0.5 °, while in the case of the forward-swept propeller, it shifts backward by 0.5 °. Therefore, aeroacoustic optimization requires the consideration of propeller deformation. Y1 - 2023 U6 - https://doi.org/10.2514/6.2023-0210 N1 - Session: Propeller, Open Rotor, and Rotorcraft Noise II AIAA SCITECH 2023 Forum, 23-27 January 2023, National Harbor, MD & Online PB - AIAA CY - Reston, Va. ER - TY - JOUR A1 - Helsper, Christoph A1 - Nießner, R. T1 - On the Influence of the Vapour Substance on the Behaviour of an Expansion Type Condensation Nucleus Counter JF - Journal of Aerosol Science. 16 (1985), H. 5 Y1 - 1985 SN - 0021-8502 SP - 457 EP - 461 ER - TY - JOUR A1 - Blome, Hans-Joachim A1 - Chu, Y. A1 - Hoell, J A1 - Priester, W. T1 - On the observational discrimination of Friedmann-Lemaître models JF - Large Scale Structures of the Universe: Proceedings of the 130th Symposium of the International Astronomical Union, dedicated to the memory of Marc A. Aaronson (1950-1987) held in Balatonfured, Hungary, June 15-20, 1987. Edited by Jean Audouze, Marie-Christine Pelletan and Sandor Szalay. Y1 - 1988 SN - 90-277-2742-2 N1 - International Astronomical Union. Symposium no. 130 SP - 517 PB - Kluwer Academic Publishers CY - Dordrecht ER - TY - JOUR A1 - Schneider, Felix A1 - Tran, Duc Hung T1 - On the relation between the fair value option and bid-ask spreads: descriptive evidence on the recognition of credit risk changes under IFRS JF - Journal of Business Economics Y1 - 2018 U6 - https://doi.org/10.1007/s11573-015-0776-2 SN - 1861-8928 VL - 85 IS - 9 SP - 1049 EP - 1081 PB - Springer CY - Berlin ER - TY - JOUR A1 - Yang, Peng-Fei A1 - Kriechbaumer, Andreas A1 - Albracht, Kirsten A1 - Sanno, Maximilian A1 - Ganse, Bergita A1 - Koy, Timmo A1 - Shang, Peng A1 - Brüggemann, Gert-Peter A1 - Müller, Lars Peter A1 - Rittweger, Jörn T1 - On the relationship between tibia torsional deformation and regional muscle contractions in habitual human exercises in vivo JF - Journal of Biomechanics Y1 - 2015 U6 - https://doi.org/10.1016/j.jbiomech.2014.12.031 SN - 0021-9290 VL - 48 IS - 3 SP - 456 EP - 464 PB - Elsevier CY - Amsterdam ER -