TY  - JOUR
A1  - Schüller, K.
A1  - Kowalski, Julia
A1  - Raback, P.
T1  - Curvilinear melting – A preliminary experimental and numerical study
JF  - International Journal of Heat and Mass Transfer
N2  - When exploring glacier ice it is often necessary to take samples or implement sensors at a certain depth underneath the glacier surface. One way of doing this is by using heated melting probes. In their common form these devices experience a straight one-dimensional downwards motion and can be modeled by standard close-contact melting theory. A recently developed melting probe however, the IceMole, achieves maneuverability by simultaneously applying a surface temperature gradient to induce a change in melting direction and controlling the effective contact-force by means of an ice screw to stabilize its change in attitude. A modeling framework for forced curvilinear melting does not exist so far and will be the content of this paper. At first, we will extend the existing theory for quasi-stationary close-contact melting to curved trajectories. We do this by introducing a rotational mode. This additional unknown in the system implies yet the need for another model closure. Within this new framework we will focus on the effect of a variable contact-force as well as different surface temperature profiles. In order to solve for melting velocity and curvature of the melting path we present both an inverse solution strategy for the analytical model, and a more general finite element framework implemented into the open source software package ELMER. Model results are discussed and compared to experimental data conducted in laboratory tests.
Y1  - 2016
U6  - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.09.046
SN  - 0017-9310
IS  - 92
SP  - 884
EP  - 892
PB  - Elsevier
CY  - Amsterdam
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  - JOUR
A1  - McArdell, Brian W.
A1  - Bartelt, Perry
A1  - Kowalski, Julia
T1  - Field observations of basal forces and fluid pore pressure in a debris flow
JF  - Geophysical Research Letters (GRL)
N2  - Using results from an 8 m2 instrumented force plate we describe field measurements of normal and shear stresses, and fluid pore pressure for a debris flow. The flow depth increased from 0.1 to 1 m within the first 12 s of flow front arrival, remained relatively constant until 100 s, and then gradually decreased to 0.5 m by 600 s. Normal and shear stresses and pore fluid pressure varied in-phase with the flow depth. Calculated bulk densities are ρb = 2000–2250 kg m−3 for the bulk flow and ρf = 1600–1750 kg m−3 for the fluid phase. The ratio of effective normal stress to shear stress yields a Coulomb basal friction angle of ϕ = 26° at the flow front. We did not find a strong correlation between the degree of agitation in the flow, estimated using the signal from a geophone on the force plate, and an assumed dynamic pore fluid pressure. Our data support the idea that excess pore-fluid pressures are long lived in debris flows and therefore contribute to their unusual mobility.
KW  - debris flow
Y1  - 2007
SN  - 0094-8276
VL  - 34
IS  - 7
ER  - 
TY  - JOUR
A1  - Lyons, W. Berry
A1  - Mikucki, Jill A.
A1  - German, Laura A.
A1  - Welch, Kathleen A.
A1  - Welch, Susan A.
A1  - Gardener, Christopher B.
A1  - Tulaczyk, Slawek M.
A1  - Pettit, Erin C.
A1  - Kowalski, Julia
A1  - Dachwald, Bernd
T1  - The Geochemistry of Englacial Brine from Taylor Glacier, Antarctica
JF  - Journal of Geophysical Research: Biogeosciences
Y1  - 2019
U6  - http://dx.doi.org/10.1029/2018JG004411
SN  - 2169-8961
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kowalski, Julia
A1  - McElwaine, Jim N.
T1  - Shallow two-component gravity-driven flows with vertical variation
JF  - Journal of Fluid Mechanics
Y1  - 2013
SN  - 0022-1120
VL  - 714
SP  - 434
EP  - 462
PB  - Cambridge Univ. Press
CY  - Cambridge
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  - Kowalski, Julia
T1  - Mathematische Murgangmodellierung
JF  - Newsletter Naturgefahren
Y1  - 2008
VL  - 2008
IS  - 2
SP  - 4
EP  - 5
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  - Heierli, Joachim
A1  - Purves, Ross S.
A1  - Felber, Andreas
A1  - Kowalski, Julia
T1  - Verification of nearest-neighbours interpretations in avalanche forecasting
JF  - Annals of Glaciology
N2  - This paper examines the positive and negative aspects of a range of interpretations of nearest-neighbours models. Measures-oriented and distributionoriented verification methods are applied to categorial, probabilistic and descriptive interpretations of nearest neighbours used operationally in avalanche forecasting in Scotland and Switzerland. The dependence of skill and accuracy measures on base rate is illustrated. The purpose of the forecast and the definition of events are important variables in determining the quality of the forecast. A discussion of the application of different interpretations in operational avalanche forecasting is presented.
KW  - avalanche
Y1  - 2004
SN  - 1727-5644
VL  - 38
IS  - 1
SP  - 84
EP  - 88
ER  - 
TY  - JOUR
A1  - German, Laura
A1  - Mikucki, Jill A.
A1  - Welch, Susan A.
A1  - Welch, Kathleen A.
A1  - Lutton, Anthony
A1  - Dachwald, Bernd
A1  - Kowalski, Julia
A1  - Heinen, Dirk
A1  - Feldmann, Marco
A1  - Francke, Gero
A1  - Espe, Clemens
A1  - Lyons, W. Berry
T1  - Validation of sampling antarctic subglacial hypersaline waters with an electrothermal ice melting probe (IceMole) for environmental analytical geochemistry
JF  - International Journal of Environmental Analytical Chemistry
N2  - Geochemical characterisation of hypersaline waters is difficult as high concentrations of salts hinder the analysis of constituents at low concentrations, such as trace metals, and the collection of samples for trace metal analysis in natural waters can be easily contaminated. This is particularly the case if samples are collected by non-conventional techniques such as those required for aquatic subglacial environments. In this paper we present the first analysis of a subglacial brine from Taylor Valley, (~ 78°S), Antarctica for the trace metals: Ba, Co, Mo, Rb, Sr, V, and U. Samples were collected englacially using an electrothermal melting probe called the IceMole. This probe uses differential heating of a copper head as well as the probe’s sidewalls and an ice screw at the melting head to move through glacier ice. Detailed blanks, meltwater, and subglacial brine samples were collected to evaluate the impact of the IceMole and the borehole pump, the melting and collection process, filtration, and storage on the geochemistry of the samples collected by this device. Comparisons between melt water profiles through the glacier ice and blank analysis, with published studies on ice geochemistry, suggest the potential for minor contributions of some species Rb, As, Co, Mn, Ni, NH4+, and NO2−+NO3− from the IceMole. The ability to conduct detailed chemical analyses of subglacial fluids collected with melting probes is critical for the future exploration of the hundreds of deep subglacial lakes in Antarctica.
Y1  - 2021
U6  - http://dx.doi.org/10.1080/03067319.2019.1704750
SN  - 0306-7319
VL  - 101
IS  - 15
SP  - 2654
EP  - 2667
PB  - Taylor & Francis
CY  - London
ER  -