TY - CHAP A1 - Waldmann, Christoph A1 - Vera, Jean-Pierre de A1 - Dachwald, Bernd A1 - Strasdeit, Henry A1 - Sohl, Frank A1 - Hanff, Hendrik A1 - Kowalski, Julia A1 - Heinen, Dirk A1 - Macht, Sabine A1 - Bestmann, Ulf A1 - Meckel, Sebastian A1 - Hildebrandt, Marc A1 - Funke, Oliver A1 - Gehrt, Jan-Jöran T1 - Search for life in ice-covered oceans and lakes beyond Earth T2 - 2018 IEEE/OES Autonomous Underwater Vehicle Workshop, Proceedings November 2018, Article number 8729761 N2 - The quest for life on other planets is closely connected with the search for water in liquid state. Recent discoveries of deep oceans on icy moons like Europa and Enceladus have spurred an intensive discussion about how these waters can be accessed. The challenge of this endeavor lies in the unforeseeable requirements on instrumental characteristics both with respect to the scientific and technical methods. The TRIPLE/nanoAUV initiative is aiming at developing a mission concept for exploring exo-oceans and demonstrating the achievements in an earth-analogue context, exploring the ocean under the ice shield of Antarctica and lakes like Dome-C on the Antarctic continent. KW - Planetary exploration KW - Jupiter KW - ice moons KW - underwater vehicle KW - Antarctica Y1 - 2018 U6 - https://doi.org/10.1109/AUV.2018.8729761 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 - Saretzki, Charlotte A1 - Bergmann, Ole A1 - Dahmann, Peter A1 - Janser, Frank A1 - Keimer, Jona A1 - Machado, Patricia A1 - Morrison, Audry A1 - Page, Henry A1 - Pluta, Emil A1 - Stübing, Felix A1 - Küpper, Thomas T1 - Are small airplanes safe with regards to COVID-19 transmission? JF - Journal of Travel Medicine Y1 - 2021 U6 - https://doi.org/10.1093/jtm/taab105 SN - 1708-8305 VL - 28 IS - 7 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - Assessment of structural mechanical effects related to torsional deformations of propellers JF - CEAS Aeronautical Journal N2 - Lifting propellers are of increasing interest for Advanced Air Mobility. All propellers and rotors are initially twisted beams, showing significant extension–twist coupling and centrifugal twisting. Torsional deformations severely impact aerodynamic performance. This paper presents a novel approach to assess different reasons for torsional deformations. A reduced-order model runs large parameter sweeps with algebraic formulations and numerical solution procedures. Generic beams represent three different propeller types for General Aviation, Commercial Aviation, and Advanced Air Mobility. Simulations include solid and hollow cross-sections made of aluminum, steel, and carbon fiber-reinforced polymer. The investigation shows that centrifugal twisting moments depend on both the elastic and initial twist. The determination of the centrifugal twisting moment solely based on the initial twist suffers from errors exceeding 5% in some cases. The nonlinear parts of the torsional rigidity do not significantly impact the overall torsional rigidity for the investigated propeller types. The extension–twist coupling related to the initial and elastic twist in combination with tension forces significantly impacts the net cross-sectional torsional loads. While the increase in torsional stiffness due to initial twist contributes to the overall stiffness for General and Commercial Aviation propellers, its contribution to the lift propeller’s stiffness is limited. The paper closes with the presentation of approximations for each effect identified as significant. Numerical evaluations are necessary to determine each effect for inhomogeneous cross-sections made of anisotropic material. KW - Lifting propeller KW - Extension–twist coupling KW - Trapeze effect KW - Centrifugal twisting moment Y1 - 2024 U6 - https://doi.org/10.1007/s13272-024-00737-7 SN - 1869-5590 (eISSN) SN - 1869-5582 N1 - Corresponding author: Felix Möhren PB - Springer CY - Wien ER - TY - JOUR A1 - Neu, Eugen A1 - Janser, Frank A1 - Khatibi, Akbar A. A1 - Braun, Carsten A1 - Orifici, Adrian C. T1 - Operational Modal Analysis of a wing excited by transonic flow JF - Aerospace Science and Technology N2 - Operational Modal Analysis (OMA) is a promising candidate for flutter testing and Structural Health Monitoring (SHM) of aircraft wings that are passively excited by wind loads. However, no studies have been published where OMA is tested in transonic flows, which is the dominant condition for large civil aircraft and is characterized by complex and unique aerodynamic phenomena. We use data from the HIRENASD large-scale wind tunnel experiment to automatically extract modal parameters from an ambiently excited wing operated in the transonic regime using two OMA methods: Stochastic Subspace Identification (SSI) and Frequency Domain Decomposition (FDD). The system response is evaluated based on accelerometer measurements. The excitation is investigated from surface pressure measurements. The forcing function is shown to be non-white, non-stationary and contaminated by narrow-banded transonic disturbances. All these properties violate fundamental OMA assumptions about the forcing function. Despite this, all physical modes in the investigated frequency range were successfully identified, and in addition transonic pressure waves were identified as physical modes as well. The SSI method showed superior identification capabilities for the investigated case. The investigation shows that complex transonic flows can interfere with OMA. This can make existing approaches for modal tracking unsuitable for their application to aircraft wings operated in the transonic flight regime. Approaches to separate the true physical modes from the transonic disturbances are discussed. Y1 - 2016 U6 - https://doi.org/10.1016/j.ast.2015.11.032 SN - 1270-9638 VL - 49 SP - 73 EP - 79 PB - Elsevier CY - Amsterdam ER -