TY  - JOUR
A1  - Mertens, Josef
A1  - Kelm, R.
A1  - Velden, A. van der
T1  - Interdisziplinäre Auslegung eines Verkehrsflugzeugflügels
JF  - DGLR-Jahrbuch 1999 Bd. 3
Y1  - 1999
N1  - DGLR-JT99-156
SP  - 1605
EP  - 1610
ER  - 
TY  - JOUR
A1  - Mertens, Josef
A1  - Klevenhusen, K. D.
A1  - Jakob, H.
T1  - Accurate Transonic Wave Drag Prediction Using Simple Physical Models
JF  - AIAA-Journal. 25 (1987), H. 6
Y1  - 1987
SN  - 0001-1452
SP  - 799
EP  - 805
ER  - 
TY  - PAT
A1  - Mertens, Josef
A1  - Lajain, Henri
T1  - Method of fabricating leading edge nose structures of aerodynamic surfaces : patent no.: US 6,415,510 B2 ; date of patent: Jul. 9, 2002
Y1  - 2002
N1  - Volltext auch in der Datenbank http://publikationen.dpma.de/ zu finden unter der Nummer US000006415510B2
PB  - United States Patent and Trademark Office
CY  - [Washington, DC]
ER  - 
TY  - JOUR
A1  - Mertens, Josef
A1  - Röger, Wolf
T1  - F-Schlepp: Problem Taumelschwingung
JF  - Aerokurier. 44 (2000), H. 10
Y1  - 2000
SN  - 0341-1281
N1  - in der Bereichsbibliothek unter der Signatur 23 Z 391-2000
SP  - 73
EP  - 73
ER  - 
TY  - PAT
A1  - Mertens, Josef
A1  - Velden, Alexander van der
A1  - Kelm, Roland
T1  - Flugzeug mit Flügeln, deren maximaler Auftrieb durch steuerbare Flügelkomponenten veränderbar ist : Offenlegungsschrift DE102004045732 ; Offenlegungstag: 30.03.2006 = Aircraft with wings whose maximum lift can be altered by controllable wing components
Y1  - 2006
N1  - Zugleich EP1791755A1. - Volltext über Datenbank: http://publikationen.dpma.de/
PB  - Deutsches Patent- und Markenamt
CY  - München
ER  - 
TY  - BOOK
A1  - Mertens, Josef
A1  - Velden, Alexander van der
A1  - Kelm, Roland
A1  - Kokan, David
T1  - Application of MDO to large subsonic transport aircraft
Y1  - 2000
N1  - Aerospace Sciences Meeting and Exhibit <38, 2000, Reno, NV> ; (AIAA Paper ; 00-0844)
PB  - American Institute of Aeronautics and Astronautics
CY  - Reston, Va.
ER  - 
TY  - JOUR
A1  - Meyer, Max-Arno
A1  - Granrath, Christian
A1  - Feyerl, Günter
A1  - Richenhagen, Johannes
A1  - Kaths, Jakob
A1  - Andert, Jakob
T1  - Closed-loop platoon simulation with cooperative intelligent transportation systems based on vehicle-to-X communication
JF  - Simulation Modelling Practice and Theory
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.simpat.2020.102173
SN  - 1569-190X
VL  - 106
IS  - Art. 102173
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Möhren, Felix
A1  - Bergmann, Ole
A1  - Janser, Frank
A1  - Braun, Carsten
T1  - On the determination of harmonic propeller loads
T2  - AIAA SCITECH 2023 Forum
N2  - 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.
Y1  - 2023
U6  - http://dx.doi.org/10.2514/6.2023-2404
N1  - AIAA SCITECH 2023 Forum, 23-27 January 2023, National Harbor, MD & Online
PB  - AIAA
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  - http://dx.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  - 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  - http://dx.doi.org/10.1016/j.ast.2015.11.032
SN  - 1270-9638
VL  - 49
SP  - 73
EP  - 79
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Neu, Eugen
A1  - Janser, Frank
A1  - Khatibi, Akbar A.
A1  - Orifici, Adrian C.
T1  - Operational modal analysis of a cantilever in a wind tunnel using optical fiber bragg grating sensors
T2  - 6th International Operational Modal Analysis Conference. IOMAC´15. 2015 May 12-14 Gijon - Spain
Y1  - 2015
U6  - http://dx.doi.org/10.13140/RG.2.1.3753.0324
ER  - 
TY  - JOUR
A1  - Neu, Eugen
A1  - Janser, Frank
A1  - Khatibi, Akbar A.
A1  - Orifici, Adrian C.
T1  - Fully Automated Operational Modal Analysis using multi-stage clustering
JF  - Mechanical Systems and Signal Processing
Y1  - 2017
U6  - http://dx.doi.org/10.1016/j.ymssp.2016.07.031
SN  - 0888-3270
VL  - Vol. 84, Part A
SP  - 308
EP  - 323
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Neu, Eugen
A1  - Janser, Frank
A1  - Khatibi, Akbar A.
A1  - Orifici, Adrian C.
T1  - Automated modal parameter-based anomaly detection under varying wind excitation
JF  - Structural Health Monitoring
N2  - Wind-induced operational variability is one of the major challenges for structural health monitoring of slender engineering structures like aircraft wings or wind turbine blades. Damage sensitive features often show an even bigger sensitivity to operational variability. In this study a composite cantilever was subjected to multiple mass configurations, velocities and angles of attack in a controlled wind tunnel environment. A small-scale impact damage was introduced to the specimen and the structural response measurements were repeated. The proposed damage detection methodology is based on automated operational modal analysis. A novel baseline preparation procedure is described that reduces the amount of user interaction to the provision of a single consistency threshold. The procedure starts with an indeterminate number of operational modal analysis identifications from a large number of datasets and returns a complete baseline matrix of natural frequencies and damping ratios that is suitable for subsequent anomaly detection. Mahalanobis distance-based anomaly detection is then applied to successfully detect the damage under varying severities of operational variability and with various degrees of knowledge about the present operational conditions. The damage detection capabilities of the proposed methodology were found to be excellent under varying velocities and angles of attack. Damage detection was less successful under joint mass and wind variability but could be significantly improved through the provision of the currently encountered operational conditions.
Y1  - 2016
U6  - http://dx.doi.org/10.1177/1475921716665803
SN  - 1475-9217
VL  - 15
IS  - 6
SP  - 1
EP  - 20
PB  - Sage
CY  - London
ER  - 
TY  - CHAP
A1  - Neu, Eugen
A1  - Janser, Frank
A1  - Khatibi, Akbar A.
A1  - Orifici, Adrian C.
T1  - In-flight vibration-based structural health monitoring of aircraft wings
T2  - 30th Congress of the internatonal council of the aeronautical sciences : 25.-30. September 2016, Daejeon, Korea
N2  - This work presents a methodology for automated
damage-sensitive feature extraction and anomaly
detection under multivariate operational variability
for in-flight assessment of wings. The
method uses a passive excitation approach, i. e.
without the need for artificial actuation. The
modal system properties (natural frequencies and
damping ratios) are used as damage-sensitive
features. Special emphasis is placed on the use
of Fiber Bragg Grating (FBG) sensing technology
and the consideration of Operational and
Environmental Variability (OEV). Measurements
from a wind tunnel investigation with a composite
cantilever equipped with FBG and piezoelectric
sensors are used to successfully detect an impact
damage. In addition, the feasibility of damage
localisation and severity estimation is evaluated
based on the coupling found between damageand
OEV-induced feature changes.
Y1  - 2016
ER  - 
TY  - CHAP
A1  - Niedermeier, H.
A1  - Clemens, J.
A1  - Kowalski, Julia
A1  - Macht, S.
A1  - Heinen, D.
A1  - Hoffmann, R.
A1  - Linder, Peter
T1  - Navigation system for a research ice probe for antarctic glaciers
T2  - IEEE/ION Position, Location and Navigation Symposium (PLANS) ; 5-8 May 2014, Monterey, Calif.
Y1  - 2014
SN  - 978-1-4799-3319-8
SP  - 959
EP  - 975
PB  - IEEE
CY  - Piscataway, NJ
ER  - 
TY  - PAT
A1  - Nonhoff, Gottfried
A1  - Wahle, Michael
T1  - Anordnung zur Dämpfung von Schwingungen an Bauwerken und Bauteilen : Offenlegungsschrift / Europäische Patentschrift
T1  - Arrangement for damping vibrations of structures or parts thereof : patent of invention
Y1  - 1990
PB  - Deutsches Patent- und Markenamt / Europäisches Patentamt
CY  - München / Den Hague
ER  - 
TY  - CHAP
A1  - Nowack, N.
A1  - Röth, Thilo
A1  - Bührig-Polaczek, A.
A1  - Klaus, G.
ED  - Hirsch, Jürgen
T1  - Advanced Sheet Metal Components Reinforced by Light Metal Cast Structures
T2  - Aluminium alloys : their physical and mechanical properties ; [proceedings of the 11th International Conference on Aluminium Alloys, 22 - 26 Sept. 2008, Aachen, Germany ; ICAA 11]
Y1  - 2008
SN  - 978-3-527-32367-8
IS  - 2
SP  - 2374
EP  - 2381
ER  - 
TY  - CHAP
A1  - Ohndorf, Andreas
A1  - Dachwald, Bernd
A1  - Seboldt, Wolfgang
A1  - Schartner, Karl-Heinz
T1  - Flight times to the heliopause using a combination of solar and radioisotope electric propulsion
T2  - 32nd International Electric Propulsion Conference
N2  - We investigate the interplanetary flight of a low-thrust space probe to the heliopause,located at a distance of about 200 AU from the Sun. Our goal was to reach this distance within the 25 years postulated by ESA for such a mission (which is less ambitious than the 15-year goal set by NASA). Contrary to solar sail concepts and combinations of allistic and electrically propelled flight legs, we have investigated whether the set flight time limit could also be kept with a combination of solar-electric propulsion and a second, RTG-powered upper stage. The used ion engine type was the RIT-22 for the first stage and the RIT-10 for the second stage. Trajectory optimization was carried out with the low-thrust optimization program InTrance, which implements the method of Evolutionary Neurocontrol,using Artificial Neural Networks for spacecraft steering and Evolutionary Algorithms to optimize the Neural Networks’ parameter set. Based on a parameter space study, in which the number of thrust units, the unit’s specific impulse, and the relative size of the solar power generator were varied, we have chosen one configuration as reference. The transfer time of this reference configuration was 29.6 years and the fastest one, which is technically
more challenging, still required 28.3 years. As all flight times of this parameter study were longer than 25 years, we further shortened the transfer time by applying a launcher-provided hyperbolic excess energy up to 49 km2/s2. The resulting minimal flight time for the reference configuration was then 27.8 years. The following, more precise optimization to a launch with the European Ariane 5 ECA rocket reduced the transfer time to 27.5 years. This is the fastest mission design of our study that is flexible enough to allow a launch every
year. The inclusion of a fly-by at Jupiter finally resulted in a flight time of 23.8 years,which is below the set transfer-time limit. However, compared to the 27.5-year transfer,this mission design has a significantly reduced launch window and mission flexibility if the
escape direction is restricted to the heliosphere’s “nose".
KW  - low-thrust trajectory optimization
KW  - heliosphere
KW  - ion propulsion
Y1  - 2011
N1  - IEPC-2011-051
32nd International Electric Propulsion Conference,September 11–15, 2011
Wiesbaden, Germany
SP  - 1
EP  - 12
ER  - 
TY  - JOUR
A1  - Olaru, Alexandra Maria
A1  - Kowalski, Julia
A1  - Sethi, Vaishali
A1  - Blümich, Bernhard
T1  - Exchange relaxometry of flow at small Péclet numbers in a glass bead pack
JF  - Journal of Magnetic Resonance (JMR)
N2  - In this paper we consider low Péclet number flow in bead packs. A series of relaxation exchange experiments has been conducted and evaluated by ILT analysis. In the resulting correlation maps, we observed a collapse of the signal and a translation towards smaller relaxation times with increasing flow rates, as well as a signal tilt with respect to the diagonal. In the discussion of the phenomena we present a mathematical theory for relaxation exchange experiments that considers both diffusive and advective transport. We perform simulations based on this theory and discuss them with respect to the conducted experiments.
KW  - NMR exchange relaxometry
KW  - Low-field NMR
Y1  - 2012
U6  - http://dx.doi.org/10.1016/j.jmr.2012.04.015
SN  - 1096-0856
VL  - 220
SP  - 32
EP  - 44
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Olaru, Alexandra Maria
A1  - Kowalski, Julia
A1  - Sethi, Vaishali
A1  - Blümich, Bernhard
T1  - Fluid Transport in Porous Media probed by Relaxation-Exchange NMR
T2  - 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.
Y1  - 2011
N1  - H12B-07; American Geophysical Union
ER  -