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  - JOUR
A1  - Fischer, Jan-Thomas
A1  - Kowalski, Julia
A1  - Pudasaini, Shiva P.
T1  - Topographic curvature effects in applied avalanche modelling
JF  - Cold Regions Science and Technology
N2  - This paper describes the implementation of topographic curvature effects within the RApid Mass MovementS (RAMMS) snow avalanche simulation toolbox. RAMMS is based on a model similar to shallow water equations with a Coulomb friction relation and the velocity dependent Voellmy drag. It is used for snow avalanche risk assessment in Switzerland. The snow avalanche simulation relies on back calculation of observed avalanches. The calibration of the friction parameters depends on characteristics of the avalanche track. The topographic curvature terms are not yet included in the above mentioned classical model. Here, we fundamentally improve this model by mathematically and physically including the topographic curvature effects. By decomposing the velocity dependent friction into a topography dependent term that accounts for a curvature enhancement in the Coulomb friction, and a topography independent contribution similar to the classical Voellmy drag, we construct a general curvature dependent frictional resistance, and thus propose new extended model equations. With three site-specific examples, we compare the apparent frictional resistance of the new approach, which includes topographic curvature effects, to the classical one. Our simulation results demonstrate substantial effects of the curvature on the flow dynamics e.g., the dynamic pressure distribution along the slope. The comparison of resistance coefficients between the two models demonstrates that the physically based extension presents an improvement to the classical approach. Furthermore a practical example highlights its influence on the pressure outline in the run out zone of the avalanche. Snow avalanche dynamics modeling natural terrain curvature centrifugal force friction coefficients.
KW  - Snow
KW  - Avalanche
Y1  - 2012
U6  - http://dx.doi.org/10.1016/j.coldregions.2012.01.005
SN  - 1872-7441
VL  - 74-75
SP  - 21
EP  - 30
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bühler, Yves
A1  - Christen, Marc
A1  - Kowalski, Julia
A1  - Bartelt, Perry
T1  - Sensitivity of snow avalanche simulations to digital elevation model quality and resolution
JF  - Annals of Glaciology
N2  - Digital elevation models (DEMs), represent the three-dimensional terrain and are the basic input for numerical snow avalanche dynamics simulations. DEMs can be acquired using topographic maps or remote-sensing technologies, such as photogrammetry or lidar. Depending on the acquisition technique, different spatial resolutions and qualities are achieved. However, there is a lack of studies that investigate the sensitivity of snow avalanche simulation algorithms to the quality and resolution of DEMs. Here, we perform calculations using the numerical avalance dynamics model RAMMS, varying the quality and spatial resolution of the underlying DEMs, while holding the simulation parameters constant. We study both channelized and open-terrain avalanche tracks with variable roughness. To quantify the variance of these simulations, we use well-documented large-scale avalanche events from Davos, Switzerland (winter 2007/08), and from our large-scale avalanche test site, Valĺee de la Sionne (winter 2005/06). We find that the DEM resolution and quality is critical for modeled flow paths, run-out distances, deposits, velocities and impact pressures. Although a spatial resolution of ~25 m is sufficient for large-scale avalanche modeling, the DEM datasets must be checked carefully for anomalies and artifacts before using them for dynamics calculations.
KW  - snow
KW  - avalanche
Y1  - 2011
SN  - 1727-5644
VL  - 52
IS  - 58
SP  - 72
EP  - 80
PB  - Cambridge University Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Dachwald, Bernd
A1  - Schmidt, Tanja D.
A1  - Seboldt, Wolfgang
A1  - Auweter-Kurtz, 
T1  - Flight Opportunities from Mars to Earth for Piloted Missions Using Continuous Thrust Propulsion / Schmidt, Tanja D. ; Dachwald, Bernd ; Seboldt, Wolfgang ; Auweter-Kurtz, Monika
Y1  - 2003
N1  - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit
20-23 July 2003, Huntsville, Alabama ; AIAA 2003-4573
SP  - 1
EP  - 9
PB  - -
ER  - 
TY  - JOUR
A1  - Krämer, Stefan
A1  - Daab, Dominique Jonas
A1  - Müller, Brigitte
A1  - Wagner, Tobias
A1  - Baader, Fabian
A1  - Hessel, Joana
A1  - Gdalewitsch, Georg
A1  - Plescher, Engelbert
A1  - Dachwald, Bernd
A1  - Wahle, Michael
A1  - Gierse, Andreas
A1  - Vetter, Rudolf
A1  - Pfützenreuter, Lysan
T1  - Development and flight-testing of a system to isolate vibrations for microgravity experiments on sounding rockets
JF  - 21st ESA Symposium on Rocket and Balloon Research
Y1  - 2013
SP  - 1
EP  - 8
ER  - 
TY  - JOUR
A1  - Funke, Harald
A1  - Dickhoff, J.
A1  - Keinz, Jan
A1  - Anis, H. A.
A1  - Parente, A.
A1  - Hendrick, P.
T1  - Experimental and numerical study of the micromix combustion principle applied for hydrogen and hydrogen-rich syngas as fuel with increased energy density for industrial gas turbine applications
JF  - Energy procedia
N2  - The Dry Low NOx (DLN) Micromix combustion principle with increased energy density is adapted for the industrial gas turbine APU GTCP 36-300 using hydrogen and hydrogen-rich syngas with a composition of 90%-Vol. hydrogen (H₂) and 10%-Vol. carbon-monoxide (CO). Experimental and numerical studies of several combustor geometries for hydrogen and syngas show the successful advance of the DLN Micromix combustion from pure hydrogen to hydrogen-rich syngas. The impact of the different fuel properties on the combustion principle and aerodynamic flame stabilization design laws, flow field, flame structure and emission characteristics is investigated by numerical analysis using a hybrid Eddy Break Up combustion model and validated against experimental results.
Y1  - 2014
U6  - http://dx.doi.org/10.1016/j.egypro.2014.12.201
SN  - 1876-6102 (E-Journal)
IS  - 61
SP  - 1736
EP  - 1739
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Schirra, Julian
A1  - Watmuff, Jonathan
A1  - Bauschat, J.-Michael
T1  - Highly non-planar lifting systems: a relative assessment of existing potential-methodologies to accurately estimate the induced drag
JF  - 32nd  AIAA Applied Aerodynamics Conference 2014 : June, 16-20 2014, Atlanta, Ga.
Y1  - 2014
SN  - 978-1-62410-288-2
U6  - http://dx.doi.org/10.2514/6.2014-2988
SP  - Publ. online
ER  - 
TY  - JOUR
A1  - Stadler, Alexander Maximilian
A1  - Garvey, Christopher J.
A1  - Embs, Jan Peter
A1  - Koza, Michael Marek
A1  - Unruh, Tobias
A1  - Artmann, Gerhard
A1  - Zaccai, Guiseppe
T1  - Picosecond dynamics in haemoglobin from different species: A quasielastic neutron scattering study
JF  - Biochimica et biophysica acta (BBA): General Subjects
Y1  - 2014
U6  - http://dx.doi.org/10.1016/j.bbagen.2014.06.007
SN  - 1872-8006 (E-Journal); 0304-4165 (Print)
VL  - 1840
IS  - 10
SP  - 2989
EP  - 2999
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Konstantinidis, Konstantinos
A1  - Flores Martinez, Claudio
A1  - Dachwald, Bernd
A1  - Ohndorf, Andreas
A1  - Dykta, Paul
A1  - Bowitz, Pascal
A1  - Rudolph, Martin
A1  - Digel, Ilya
A1  - Kowalski, Julia
A1  - Voigt, Konstantin
A1  - Förstner, Roger
T1  - A lander mission to probe subglacial water on Saturn's moon enceladus for life
JF  - Acta astronautica
Y1  - 2015
SN  - 1879-2030 (E-Journal); 0094-5765 (Print)
VL  - Vol. 106
SP  - 63
EP  - 89
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Dachwald, Bernd
A1  - Mikucki, Jill
A1  - Tulaczyk, Slawek
A1  - Digel, Ilya
A1  - Espe, Clemens
A1  - Feldmann, Marco
A1  - Francke, Gero
A1  - Kowalski, Julia
A1  - Xu, Changsheng
T1  - IceMole : A maneuverable probe for clean in situ analysis and sampling of subsurface ice and subglacial aquatic ecosystems
JF  - Annals of Glaciology
N2  - There is significant interest in sampling subglacial environments for geobiological studies, but they are difficult to access. Existing ice-drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. The IceMole is a maneuverable subsurface ice probe for clean in situ analysis and sampling of glacial ice and subglacial materials. The design is based on the novel concept of combining melting and mechanical propulsion. It can change melting direction by differential heating of the melting head and optional side-wall heaters. The first two prototypes were successfully tested between 2010 and 2012 on glaciers in Switzerland and Iceland. They demonstrated downward, horizontal and upward melting, as well as curve driving and dirt layer penetration. A more advanced probe is currently under development as part of the Enceladus Explorer (EnEx) project. It offers systems for obstacle avoidance, target detection, and navigation in ice. For the EnEx-IceMole, we will pay particular attention to clean protocols for the sampling of subglacial materials for biogeochemical analysis. We plan to use this probe for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, with return of a subglacial brine sample.
KW  - Antarctic Glaciology
KW  - Extraterrestrial Glaciology
KW  - Glaciological instruments and methods
KW  - Subclacial exploration
KW  - Subglacial lakes
Y1  - 2014
U6  - http://dx.doi.org/10.3189/2014AoG65A004
SN  - 1727-5644
VL  - 55
IS  - 65
SP  - 14
EP  - 22
PB  - Cambridge University Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Mathiak, Gerhard
A1  - Plescher, Engelbert
A1  - Willnecker, Rainer
T1  - Liquid metal diffusion experiments in microgravity - Vibrational effects
JF  - Measurement science and technology
Y1  - 2005
U6  - http://dx.doi.org/10.1088/0957-0233/16/2/003
SN  - 0957-0233
VL  - Vol. 16
IS  - No. 2
SP  - 336
ER  - 
TY  - JOUR
A1  - Mathiak, Gerhard
A1  - Willnecker, Rainer
A1  - Plescher, Engelbert
T1  - Vibrational effects on diffusion experiments
JF  - Microgravity science and technology : international journal for microgravity research and applications
Y1  - 2005
SN  - 0938-0108
VL  - Vol. 15
IS  - No. 1
SP  - 295
EP  - 300
ER  - 
TY  - JOUR
A1  - Seifarth, Volker
A1  - Goßmann, Matthias
A1  - Grosse, J. O.
A1  - Becker, C.
A1  - Heschel, I.
A1  - Artmann, Gerhard
A1  - Temiz Artmann, Aysegül
T1  - Development of a Bioreactor to Culture Tissue Engineered Ureters Based on the Application of Tubular OPTIMAIX 3D Scaffolds
JF  - Urologia Internationalis
Y1  - 2015
U6  - http://dx.doi.org/10.1159/000368419
SN  - 0042-1138
VL  - 2015
IS  - 95
SP  - 106
EP  - 113
PB  - Karger
CY  - Basel
ER  - 
TY  - JOUR
A1  - Haj Ayed, A.
A1  - Kusterer, K.
A1  - Funke, Harald
A1  - Keinz, Jan
A1  - Striegan, Constantin
A1  - Bohn, D.
T1  - Experimental and numerical investigations of the dry-low-NOx hydrogen micromix combustion chamber of an industrial gas turbine
JF  - Propulsion and power research
Y1  - 2015
U6  - http://dx.doi.org/10.1016/j.jppr.2015.07.005
SN  - 2212-540X
VL  - Vol. 4
IS  - Iss. 3
SP  - 123
EP  - 131
ER  - 
TY  - JOUR
A1  - Haj Ayed, A.
A1  - Kusterer, K.
A1  - Funke, Harald
A1  - Keinz, Jan
A1  - Striegan, Constantin
A1  - Bohn, D.
T1  - Improvement study for the dry-low-NOx hydrogen micromix combustion technology
JF  - Propulsion and power research
Y1  - 2015
U6  - http://dx.doi.org/10.1016/j.jppr.2015.07.003
SN  - 2212-540X
VL  - Vol. 4
IS  - Iss. 3
SP  - 132
EP  - 140
ER  - 
TY  - JOUR
A1  - Bindal, Gaurav
A1  - Sharma, Sparsh
A1  - Janser, Frank
A1  - Neu, Eugen
T1  - Detailed analysis of variables affecting wing kinematics of bat flight
JF  - SAE International Journal of Aerospace
Y1  - 2013
U6  - http://dx.doi.org/10.4271/2013-01-9003
SN  - 1946-3901
VL  - 6
IS  - 2
SP  - 811
EP  - 818
ER  - 
TY  - JOUR
A1  - Kowalski, Julia
A1  - Linder, Peter
A1  - Zierke, S.
A1  - Wulfen, B. van
A1  - Clemens, J.
A1  - Konstantinidis, K.
A1  - Ameres, G.
A1  - Hoffmann, R.
A1  - Mikucki, J.
A1  - Tulaczyk, S.
A1  - Funke, O.
A1  - Blandfort, D.
A1  - Espe, Clemens
A1  - Feldmann, Marco
A1  - Francke, Gero
A1  - Hiecker, S.
A1  - Plescher, Engelbert
A1  - Schöngarth, Sarah
A1  - Dachwald, Bernd
A1  - Digel, Ilya
A1  - Artmann, Gerhard
A1  - Eliseev, D.
A1  - Heinen, D.
A1  - Scholz, F.
A1  - Wiebusch, C.
A1  - Macht, S.
A1  - Bestmann, U.
A1  - Reineking, T.
A1  - Zetzsche, C.
A1  - Schill, K.
A1  - Förstner, R.
A1  - Niedermeier, H.
A1  - Szumski, A.
A1  - Eissfeller, B.
A1  - Naumann, U.
A1  - Helbing, K.
T1  - Navigation technology for exploration of glacier ice with maneuverable melting probes
JF  - Cold Regions Science and Technology
N2  - The Saturnian moon Enceladus with its extensive water bodies underneath a thick ice sheet cover is a potential candidate for extraterrestrial life. Direct exploration of such extraterrestrial aquatic ecosystems requires advanced access and sampling technologies with a high level of autonomy. A new technological approach has been developed as part of the collaborative research project Enceladus Explorer (EnEx). The concept is based upon a minimally invasive melting probe called the IceMole. The force-regulated, heater-controlled IceMole is able to travel along a curved trajectory as well as upwards. Hence, it allows maneuvers which may be necessary for obstacle avoidance or target selection. Maneuverability, however, necessitates a sophisticated on-board navigation system capable of autonomous operations. The development of such a navigational system has been the focal part of the EnEx project. The original IceMole has been further developed to include relative positioning based on in-ice attitude determination, acoustic positioning, ultrasonic obstacle and target detection integrated through a high-level sensor fusion. This paper describes the EnEx technology and discusses implications for an actual extraterrestrial mission concept.
Y1  - 2016
U6  - http://dx.doi.org/10.1016/j.coldregions.2015.11.006
SN  - 0165-232X
IS  - 123
SP  - 53
EP  - 70
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Grundmann, Jan Thimo
A1  - Dachwald, Bernd
A1  - Grimm, Christian D.
A1  - Kahle, Ralph
A1  - Koch, Aaron Dexter
A1  - Krause, Christian
A1  - Lange, Caroline
A1  - Quantius, Dominik
A1  - Ulamec, Stephan
T1  - Spacecraft for Hypervelocity Impact Research – An Overview of Capabilities, Constraints and the Challenges of Getting There
JF  - Procedia Engineering
Y1  - 2015
U6  - http://dx.doi.org/10.1016/j.proeng.2015.04.021
SN  - 1877-7058
N1  - Proceedings of the 2015 Hypervelocity Impact Symposium (HVIS 2015)
VL  - Vol. 103
SP  - 151
EP  - 158
PB  - Elsevier
CY  - Amsterdam
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  - 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  -