@inproceedings{GrundmannBauerBodenetal.2019, author = {Grundmann, Jan Thimo and Bauer, Waldemar and Boden, Ralf and Ceriotti, Matteo and Chand, Suditi and Cordero, Federico and Dachwald, Bernd and Dumont, Etienne and Grimm, Christian D. and Heiligers, Jeannette and Herč{\´i}k, David and H{\´e}rique, Alain and Ho, Tra-Mi and Jahnke, Rico and Kofman, Wlodek and Lange, Caroline and Lichtenheldt, Roy and McInnes, Colin and Meß, Jan-Gerd and Mikschl, Tobias and Mikulz, Eugen and Montenegro, Sergio and Moore, Iain and Pelivan, Ivanka and Peloni, Alessandro and Plettemeier, Dirk and Quantius, Dominik and Reershemius, Siebo and Renger, Thomas and Riemann, Johannes and Rogez, Yves and Ruffer, Michael and Sasaki, Kaname and Schmitz, Nicole and Seboldt, Wolfgang and Seefeldt, Patric and Spietz, Peter and Spr{\"o}witz, Tom and Sznajder, Maciej and T{\´o}th, Norbert and Vergaaij, Merel and Viavattene, Giulia and Wejmo, Elisabet and Wiedemann, Carsten and Wolff, Friederike and Ziach, Christian}, title = {Flights are ten a sail - Re-use and commonality in the design and system engineering of small spacecraft solar sail missions with modular hardware for responsive and adaptive exploration}, series = {70th International Astronautical Congress (IAC)}, booktitle = {70th International Astronautical Congress (IAC)}, isbn = {9781713814856}, pages = {1 -- 7}, year = {2019}, language = {en} } @incollection{ReimerWellmerBraunetal.2009, author = {Reimer, Lars and Wellmer, Georg and Braun, Carsten and Ballmann, Josef}, title = {Computational methods for aero-structural analysis and optimisation of aircrafts based on reduced-order structural models}, series = {MEGADESIGN and MegaOpt - German initiatives for aerodynamic simulation and optimization in aircraft design. Results of the closing symposium of the MEGADESIGN and MegaOpt projects, Braunschweig, Germany, 23 - 24 May, 2007 / Norbert Kroll ... (Eds.) Notes on numerical fluid mechanics and multidisciplinary design. Vol. 107}, booktitle = {MEGADESIGN and MegaOpt - German initiatives for aerodynamic simulation and optimization in aircraft design. Results of the closing symposium of the MEGADESIGN and MegaOpt projects, Braunschweig, Germany, 23 - 24 May, 2007 / Norbert Kroll ... (Eds.) Notes on numerical fluid mechanics and multidisciplinary design. Vol. 107}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-642-04092-4}, pages = {135 -- 150}, year = {2009}, abstract = {In this part of the MEGADESIGN project, aeroelastic effects are introduced into the aerodynamic analysis of aircrafts by coupling DLR's flow solvers TAU and FLOWer to a Timoshenko-beam solver. The emerging aeroelastic solvers and a method for the automatic identification of Timoshenko-beam models for wing-box structures were integrated into a simulation environment enabling the combined optimisation of aerodynamic wing shape and structure.}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Evolutionary Neurocontrol: A Smart Method for Global Optimization of Low-Thrust Trajectories}, series = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, journal = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, publisher = {American Inst. of Aeronautics and Astronautics}, address = {Reston, Va.}, pages = {2 CD-ROMs}, year = {2004}, language = {en} } @article{HeiligersSchoutetensDachwald2021, author = {Heiligers, Jeannette and Schoutetens, Frederic and Dachwald, Bernd}, title = {Photon-sail equilibria in the alpha centauri system}, series = {Journal of Guidance, Control, and Dynamics}, volume = {44}, journal = {Journal of Guidance, Control, and Dynamics}, number = {5}, issn = {1533-3884}, doi = {10.2514/1.G005446}, pages = {1053 -- 1061}, year = {2021}, language = {en} } @article{KerpenBungValeroetal.2017, author = {Kerpen, Nils B. and Bung, Daniel Bernhard and Valero, Daniel and Schlurmann, Torsten}, title = {Energy dissipation within the wave run-up at stepped revetments}, series = {Journal of Ocean University of China}, volume = {16}, journal = {Journal of Ocean University of China}, number = {4}, publisher = {Springer}, address = {Berlin}, issn = {1993-5021}, doi = {10.1007/s11802-017-3355-z}, pages = {649 -- 654}, year = {2017}, language = {en} } @article{ValeroBung2016, author = {Valero, Daniel and Bung, Daniel Bernhard}, title = {Development of the interfacial air layer in the non-aerated region of high-velocity spillway flows: Instabilities growth, entrapped air and influence on the self-aeration onset}, series = {International Journal of Multiphase Flow}, volume = {84}, journal = {International Journal of Multiphase Flow}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-9322}, doi = {10.1016/j.ijmultiphaseflow.2016.04.012}, pages = {66 -- 74}, year = {2016}, abstract = {Self-aeration is traditionally explained by the water turbulent boundary layer outer edge intersection with the free surface. This paper presents a discussion on the commonly accepted hypothesis behind the computation of the critical point of self-aeration in spillway flows and a new formulation is proposed based on the existence of a developing air flow over the free surface. Upstream of the inception point of self-aeration, some surface roughening has been often reported in previous studies which consequently implies some entrapped air transport and air-water flows coupling. Such air flow is proven in this study by presenting measured air velocities and computing the air boundary layer thickness for a 1V:2H smooth chute flow. Additionally, the growth rate of free surface waves has been analysed by means of Ultrasonic Sensors measurements, obtaining also the entrapped air concentration. High-speed camera imaging has been used for qualitative study of the flow perturbations.}, language = {en} } @incollection{BialonskiLehnertz2013, author = {Bialonski, Stephan and Lehnertz, Klaus}, title = {From time series to complex networks: an overview}, series = {Recent Advances in Predicting and Preventing Epileptic Seizures: Proceedings of the 5th International Workshop on Seizure Prediction}, booktitle = {Recent Advances in Predicting and Preventing Epileptic Seizures: Proceedings of the 5th International Workshop on Seizure Prediction}, isbn = {978-981-4525-36-7}, doi = {10.1142/9789814525350_0010}, pages = {132 -- 147}, year = {2013}, abstract = {The network approach towards the analysis of the dynamics of complex systems has been successfully applied in a multitude of studies in the neurosciences and has yielded fascinating insights. With this approach, a complex system is considered to be composed of different constituents which interact with each other. Interaction structures can be compactly represented in interaction networks. In this contribution, we present a brief overview about how interaction networks are derived from multivariate time series, about basic network characteristics, and about challenges associated with this analysis approach.}, language = {en} } @inproceedings{BungSchlenkhoff2010, author = {Bung, Daniel Bernhard and Schlenkhoff, Andreas}, title = {Self-aerated skimming flow on embankment stepped spillways : the effect of additional micro-roughness on energy dissipation and oxygen transfer}, series = {Proceedings from first IAHR European congress : May 2010, Edinburgh}, booktitle = {Proceedings from first IAHR European congress : May 2010, Edinburgh}, publisher = {Heriot-Watt University, School of the Built Environment}, address = {Edinburgh}, organization = {International Association for Hydraulic Engineering and Research}, isbn = {9780956595102}, pages = {Artikelkennnummer HSIIId}, year = {2010}, language = {en} } @article{KozhalakovaZhubanovaMansurovetal.2010, author = {Kozhalakova, A. A. and Zhubanova, Azhar A. and Mansurov, Z. A. and Digel, Ilya and Tazhibayeva, S. M. and Artmann, Gerhard and Temiz Artmann, Ayseg{\"u}l}, title = {Adsorption of bacterial lipopolysaccharides on carbonized rice shell}, series = {Science of Central Asia (2010)}, journal = {Science of Central Asia (2010)}, pages = {50 -- 54}, year = {2010}, language = {en} } @article{MoehrenBergmannJanseretal.2024, author = {M{\"o}hren, Felix and Bergmann, Ole and Janser, Frank and Braun, Carsten}, title = {Assessment of structural mechanical effects related to torsional deformations of propellers}, series = {CEAS Aeronautical Journal}, journal = {CEAS Aeronautical Journal}, publisher = {Springer}, address = {Wien}, issn = {1869-5590 (eISSN)}, doi = {10.1007/s13272-024-00737-7}, pages = {22 Seiten}, year = {2024}, abstract = {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.}, language = {en} } @article{NeuJanserKhatibietal.2016, author = {Neu, Eugen and Janser, Frank and Khatibi, Akbar A. and Braun, Carsten and Orifici, Adrian C.}, title = {Operational Modal Analysis of a wing excited by transonic flow}, series = {Aerospace Science and Technology}, volume = {49}, journal = {Aerospace Science and Technology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1270-9638}, doi = {10.1016/j.ast.2015.11.032}, pages = {73 -- 79}, year = {2016}, abstract = {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.}, language = {en} } @article{NgamgaBialonskiMarwanetal.2016, author = {Ngamga, Eulalie Joelle and Bialonski, Stephan and Marwan, Norbert and Kurths, J{\"u}rgen and Geier, Christian and Lehnertz, Klaus}, title = {Evaluation of selected recurrence measures in discriminating pre-ictal and inter-ictal periods from epileptic EEG data}, series = {Physics Letters A}, volume = {380}, journal = {Physics Letters A}, number = {16}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0375-9601}, doi = {10.1016/j.physleta.2016.02.024}, pages = {1419 -- 1425}, year = {2016}, abstract = {We investigate the suitability of selected measures of complexity based on recurrence quantification analysis and recurrence networks for an identification of pre-seizure states in multi-day, multi-channel, invasive electroencephalographic recordings from five epilepsy patients. We employ several statistical techniques to avoid spurious findings due to various influencing factors and due to multiple comparisons and observe precursory structures in three patients. Our findings indicate a high congruence among measures in identifying seizure precursors and emphasize the current notion of seizure generation in large-scale epileptic networks. A final judgment of the suitability for field studies, however, requires evaluation on a larger database.}, language = {en} } @inproceedings{ThomaFisherBertrandetal.2020, author = {Thoma, Andreas and Fisher, Alex and Bertrand, Olivier and Braun, Carsten}, title = {Evaluation of possible flight strategies for close object evasion from bumblebee experiments}, series = {Living Machines 2020: Biomimetic and Biohybrid Systems}, booktitle = {Living Machines 2020: Biomimetic and Biohybrid Systems}, editor = {Vouloutsi, Vasiliki and Mura, Anna and Tauber, Falk and Speck, Thomas and Prescott, Tony J. and Verschure, Paul F. M. J.}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-64312-6}, doi = {10.1007/978-3-030-64313-3_34}, pages = {354 -- 365}, year = {2020}, 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} } @article{ThomaThomessenGardietal.2023, author = {Thoma, Andreas and Thomessen, Karolin and Gardi, Alessandro and Fisher, A. and Braun, Carsten}, title = {Prioritising paths: An improved cost function for local path planning for UAV in medical applications}, series = {The Aeronautical Journal}, journal = {The Aeronautical Journal}, number = {First View}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {0001-9240 (Print)}, doi = {10.1017/aer.2023.68}, pages = {1 -- 18}, year = {2023}, abstract = {Even the shortest flight through unknown, cluttered environments requires reliable local path planning algorithms to avoid unforeseen obstacles. The algorithm must evaluate alternative flight paths and identify the best path if an obstacle blocks its way. Commonly, weighted sums are used here. This work shows that weighted Chebyshev distances and factorial achievement scalarising functions are suitable alternatives to weighted sums if combined with the 3DVFH* local path planning algorithm. Both methods considerably reduce the failure probability of simulated flights in various environments. The standard 3DVFH* uses a weighted sum and has a failure probability of 50\% in the test environments. A factorial achievement scalarising function, which minimises the worst combination of two out of four objective functions, reaches a failure probability of 26\%; A weighted Chebyshev distance, which optimises the worst objective, has a failure probability of 30\%. These results show promise for further enhancements and to support broader applicability.}, language = {en} } @inproceedings{ValeroBungCrookstonetal.2016, author = {Valero, Daniel and Bung, Daniel Bernhard and Crookston, B. M. and Matos, J.}, title = {Numerical investigation of USBR type III stilling basin performance downstream of smooth and stepped spillways}, series = {Hydraulic Structures and Water System Management. 6th IAHR International Symposium on Hydraulic Structures, Portland, OR, 27-30 June 2016}, booktitle = {Hydraulic Structures and Water System Management. 6th IAHR International Symposium on Hydraulic Structures, Portland, OR, 27-30 June 2016}, editor = {Crookston, B. and Tullis, B.}, isbn = {978-1-884575-75-4}, doi = {10.15142/T340628160853}, pages = {635 -- 646}, year = {2016}, language = {en} } @article{Bung2013, author = {Bung, Daniel Bernhard}, title = {Non-intrusive detection of air-water surface roughness in self-aerated chute flows}, series = {Journal of hydraulic research}, volume = {Vol. 51}, journal = {Journal of hydraulic research}, number = {Iss. 3}, publisher = {Taylor \& Francis}, address = {London}, issn = {1814-2079 (E-Journal); 0022-1686 (Print)}, pages = {322 -- 329}, year = {2013}, language = {en} } @article{MuellerBeckersMussmannetal.2018, author = {M{\"u}ller, Janina and Beckers, Mario and Mußmann, Nina and Bongaerts, Johannes and B{\"u}chs, Jochen}, title = {Elucidation of auxotrophic deficiencies of Bacillus pumilus DSM 18097 to develop a defined minimal medium}, series = {Microbial Cell Factories}, volume = {17}, journal = {Microbial Cell Factories}, number = {1}, publisher = {BioMed Central}, issn = {1475-2859}, doi = {10.1186/s12934-018-0956-1}, pages = {Article No. 106}, year = {2018}, abstract = {Background Culture media containing complex compounds like yeast extract or peptone show numerous disadvantages. The chemical composition of the complex compounds is prone to significant variations from batch to batch and quality control is difficult. Therefore, the use of chemically defined media receives more and more attention in commercial fermentations. This concept results in better reproducibility, it simplifies downstream processing of secreted products and enable rapid scale-up. Culturing bacteria with unknown auxotrophies in chemically defined media is challenging and often not possible without an extensive trial-and-error approach. In this study, a respiration activity monitoring system for shake flasks and its recent version for microtiter plates were used to clarify unknown auxotrophic deficiencies in the model organism Bacillus pumilus DSM 18097. Results Bacillus pumilus DSM 18097 was unable to grow in a mineral medium without the addition of complex compounds. Therefore, a rich chemically defined minimal medium was tested containing basically all vitamins, amino acids and nucleobases, which are essential ingredients of complex components. The strain was successfully cultivated in this medium. By monitoring of the respiration activity, nutrients were supplemented to and omitted from the rich chemically defined medium in a rational way, thus enabling a systematic and fast determination of the auxotrophic deficiencies. Experiments have shown that the investigated strain requires amino acids, especially cysteine or histidine and the vitamin biotin for growth. Conclusions The introduced method allows an efficient and rapid identification of unknown auxotrophic deficiencies and can be used to develop a simple chemically defined tailor-made medium. B. pumilus DSM 18097 was chosen as a model organism to demonstrate the method. However, the method is generally suitable for a wide range of microorganisms. By combining a systematic combinatorial approach based on monitoring the respiration activity with cultivation in microtiter plates, high throughput experiments with high information content can be conducted. This approach facilitates media development, strain characterization and cultivation of fastidious microorganisms in chemically defined minimal media while simultaneously reducing the experimental effort.}, language = {en} } @article{KochBoehnischVerdoncketal.2024, author = {Koch, Christopher and B{\"o}hnisch, Nils and Verdonck, Hendrik and Hach, Oliver and Braun, Carsten}, title = {Comparison of unsteady low- and mid-fidelity propeller aerodynamic methods for whirl flutter applications}, series = {Applied Sciences}, volume = {14}, journal = {Applied Sciences}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2076-3417}, doi = {10.3390/app14020850}, pages = {1 -- 28}, year = {2024}, abstract = {Aircraft configurations with propellers have been drawing more attention in recent times, partly due to new propulsion concepts based on hydrogen fuel cells and electric motors. These configurations are prone to whirl flutter, which is an aeroelastic instability affecting airframes with elastically supported propellers. It commonly needs to be mitigated already during the design phase of such configurations, requiring, among other things, unsteady aerodynamic transfer functions for the propeller. However, no comprehensive assessment of unsteady propeller aerodynamics for aeroelastic analysis is available in the literature. This paper provides a detailed comparison of nine different low- to mid-fidelity aerodynamic methods, demonstrating their impact on linear, unsteady aerodynamics, as well as whirl flutter stability prediction. Quasi-steady and unsteady methods for blade lift with or without coupling to blade element momentum theory are evaluated and compared to mid-fidelity potential flow solvers (UPM and DUST) and classical, derivative-based methods. Time-domain identification of frequency-domain transfer functions for the unsteady propeller hub loads is used to compare the different methods. Predictions of the minimum required pylon stiffness for stability show good agreement among the mid-fidelity methods. The differences in the stability predictions for the low-fidelity methods are higher. Most methods studied yield a more unstable system than classical, derivative-based whirl flutter analysis, indicating that the use of more sophisticated aerodynamic modeling techniques might be required for accurate whirl flutter prediction.}, language = {en} } @inproceedings{TomicPennaDeJongetal.2020, author = {Tomic, Igor and Penna, Andrea and DeJong, Matthew and Butenweg, Christoph and Senaldi, Ilaria and Guerrini, Gabriele and Malomo, Daniele and Beyer, Katrin}, title = {Blind predictions of shake table testing of aggregate masonry buildings}, series = {Proceedings of the 17th World Conference on Earthquake Engineering}, booktitle = {Proceedings of the 17th World Conference on Earthquake Engineering}, year = {2020}, abstract = {In many historical centers in Europe, stone masonry is part of building aggregates, which developed when the layout of the city or village was densified. The analysis of such building aggregates is very challenging and modelling guidelines missing. Advances in the development of analysis methods have been impeded by the lack of experimental data on the seismic response of such aggregates. The SERA project AIMS (Seismic Testing of Adjacent Interacting Masonry Structures) provides such experimental data by testing an aggregate of two buildings under two horizontal components of dynamic excitation. With the aim to advance the modelling of unreinforced masonry aggregates, a blind prediction competition is organized before the experimental campaign. Each group has been provided a complete set of construction drawings, material properties, testing sequence and the list of measurements to be reported. The applied modelling approaches span from equivalent frame models to Finite Element models using shell elements and discrete element models with solid elements. This paper compares the first entries, regarding the modelling approaches, results in terms of base shear, roof displacements, interface openings, and the failure modes.}, language = {en} }