@article{FingerBilBraun2019,
  author    = {Finger, Felix and Bil, Cees and Braun, Carsten},
  title     = {Initial Sizing Methodology for Hybrid-Electric General Aviation Aircraft},
  series = {Journal of Aircraft},
  volume    = {57},
  journal   = {Journal of Aircraft},
  number    = {2},
  issn      = {1533-3868},
  doi       = {10.2514/1.C035428},
  pages     = {245 -- 255},
  year      = {2019},
  language  = {en}
}
@inproceedings{LudowicyRingsFingeretal.2019,
  author    = {Ludowicy, Jonas and Rings, Ren{\´e} and Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Impact of Propulsion Technology Levels on the Sizing and Energy Consumption for Serial HybridElectric General Aviation Aircraft},
  series = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  booktitle = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  pages     = {14 Seiten},
  year      = {2019},
  language  = {en}
}
@inproceedings{RingsLudowicyFingeretal.2019,
  author    = {Rings, Ren{\´e} and Ludowicy, Jonas and Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Sensitivity Analysis of General Aviation Aircraft with Parallel Hybrid-Electric Propulsion Systems},
  series = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  booktitle = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  pages     = {14 Seiten},
  year      = {2019},
  language  = {en}
}
@inproceedings{FingerBraunBil2019,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Impact of Engine Failure Constraints on the Initial Sizing of Hybrid-Electric GA Aircraft},
  series = {AIAA Scitech 2019 Forum},
  booktitle = {AIAA Scitech 2019 Forum},
  doi       = {10.2514/6.2019-1812},
  year      = {2019},
  language  = {en}
}
@inproceedings{GoettenFingerHavermannetal.2019,
  author    = {G{\"o}tten, Falk and Finger, Felix and Havermann, Marc and Braun, Carsten and Marino, Matthew and Bil, Cees},
  title     = {A highly automated method for simulating airfoil characteristics at low Reynolds number using a RANS - transition approach},
  series = {Deutscher Luft- und Raumfahrtkongress - DLRK 2019. Darmstadt, Germany},
  booktitle = {Deutscher Luft- und Raumfahrtkongress - DLRK 2019. Darmstadt, Germany},
  doi       = {10.25967/490026},
  pages     = {1 -- 14},
  year      = {2019},
  language  = {en}
}
@inproceedings{FingerGoettenBraunetal.2019,
  author    = {Finger, Felix and G{\"o}tten, Falk and Braun, Carsten and Bil, Cees},
  title     = {Mass, Primary Energy, and Cost - The Impact of Optimization Objectives on the Initial Sizing of Hybrid-Electric General Aviation Aircraft},
  series = {Deutscher Luft- und Raumfahrtkongress 2019, DLRK 2019. Darmstadt, Germany},
  booktitle = {Deutscher Luft- und Raumfahrtkongress 2019, DLRK 2019. Darmstadt, Germany},
  doi       = {10.25967/490012},
  pages     = {1 -- 17},
  year      = {2019},
  language  = {en}
}
@article{GoettenHavermannBraunetal.2020,
  author    = {G{\"o}tten, Falk and Havermann, Marc and Braun, Carsten and Marino, Matthew and Bil, Cees},
  title     = {Airfoil drag at low-to-medium reynolds numbers: A novel estimation method},
  series = {AIAA Journal},
  volume    = {58},
  journal   = {AIAA Journal},
  number    = {7},
  publisher = {AIAA},
  address   = {Reston, Va.},
  issn      = {1533-385X},
  doi       = {10.2514/1.J058983},
  pages     = {2791 -- 2805},
  year      = {2020},
  abstract  = {This paper presents a novel method for airfoil drag estimation at Reynolds numbers between 4×10⁵ and 4×10⁶. The novel method is based on a systematic study of 40 airfoils applying over 600 numerical simulations and considering natural transition. The influence of the airfoil thickness-to-chord ratio, camber, and freestream Reynolds number on both friction and pressure drag is analyzed in detail. Natural transition significantly affects drag characteristics and leads to distinct drag minima for different Reynolds numbers and thickness-to-chord ratios. The results of the systematic study are used to develop empirical correlations that can accurately predict an airfoil drag at low-lift conditions. The new approach estimates a transition location based on airfoil thickness-to-chord ratio, camber, and Reynolds number. It uses the transition location in a mixed laminar-turbulent skin-friction calculation, and corrects the skin-friction coefficient for separation effects. Pressure drag is estimated separately based on correlations of thickness-to-chord ratio, camber, and Reynolds number. The novel method shows excellent accuracy when compared with wind-tunnel measurements of multiple airfoils. It is easily integrable into existing aircraft design environments and is highly beneficial in the conceptual design stage.},
  language  = {en}
}
@techreport{ThomaLaarmannMerkensetal.2020,
  author    = {Thoma, Andreas and Laarmann, Lukas and Merkens, Torsten and Franzke, Till and M{\"o}hren, Felix and Buttermann, Lilly and van der Weem, Dirk and Fischer, Maximilian and Misch, Philipp and B{\"o}hme, Mirijam and R{\"o}th, Thilo and Hebel, Christoph and Ritz, Thomas and Franke, Marina and Braun, Carsten},
  title     = {Entwicklung eines intermodalen Mobilit{\"a}tskonzeptes f{\"u}r die Pilotregion NRW/Rhein-Maas Euregio und Schaffung voller Kundenakzeptanz durch Transfer von Standards aus dem PKW-Bereich auf ein Flugtaxi : Schlussbericht : Projektakronym: SkyCab (Kategorie B) : Laufzeit in Monaten: 6 : Hauptthema: Kategorie B: Innovative Ideen mit Bezug zu UAS/Flugtaxis},
  publisher = {FH Aachen},
  address   = {Aachen},
  pages     = {97 Seiten},
  year      = {2020},
  language  = {de}
}
@article{BergmannMoehrenBraunetal.2023,
  author    = {Bergmann, Ole and M{\"o}hren, Felix and Braun, Carsten and Janser, Frank},
  title     = {On the influence of elasticity on swept propeller noise},
  series = {AIAA SCITECH 2023 Forum},
  journal   = {AIAA SCITECH 2023 Forum},
  publisher = {AIAA},
  doi       = {10.2514/6.2023-0210},
  year      = {2023},
  abstract  = {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.},
  language  = {en}
}
@inproceedings{MoehrenBergmannJanseretal.2023,
  author    = {M{\"o}hren, Felix and Bergmann, Ole and Janser, Frank and Braun, Carsten},
  title     = {On the determination of harmonic propeller loads},
  series = {AIAA SCITECH 2023 Forum},
  booktitle = {AIAA SCITECH 2023 Forum},
  publisher = {AIAA},
  doi       = {10.2514/6.2023-2404},
  pages     = {12 Seiten},
  year      = {2023},
  abstract  = {Dynamic loads significantly impact the structural design of propeller blades due to fatigue and static strength. Since propellers are elastic structures, deformations and aerodynamic loads are coupled. In the past, propeller manufacturers established procedures to determine unsteady aerodynamic loads and the structural response with analytical steady-state calculations. According to the approach, aeroelastic coupling primarily consists of torsional deformations. They neglect bending deformations, deformation velocities, and inertia terms. This paper validates the assumptions above for a General Aviation propeller and a lift propeller for urban air mobility or large cargo drones. Fully coupled reduced-order simulations determine the dynamic loads in the time domain. A quasi-steady blade element momentum approach transfers loads to one-dimensional finite beam elements. The simulation results are in relatively good agreement with the analytical method for the General Aviation propeller but show increasing errors for the slender lift propeller. The analytical approach is modified to consider the induced velocities. Still, inertia and velocity proportional terms play a significant role for the lift propeller due to increased elasticity. The assumption that only torsional deformations significantly impact the dynamic loads of propellers is not valid. Adequate determination of dynamic loads of such designs requires coupled aeroelastic simulations or advanced analytical procedures.},
  language  = {en}
}