scholarly journals A Movie Film Illustrating the Numerical Modelling of Periodically Surging Ice Masses

1976 ◽  
Vol 16 (74) ◽  
pp. 304-305
Author(s):  
W.F. Budd ◽  
B.J. Mcinnes
Keyword(s):  
Steady State ◽  
Flow Line ◽  
Three Dimensional ◽  
Surface Profile ◽  
High Viscosity ◽  
Ice Cap ◽  
Section Shape ◽  
Measured Profile ◽  
Full Temperature ◽  
Line Patterns

AbstractA general two-dimensional numerical model for a typical flow line of a glacier or ice cap has been developed which results in periodical surging for certain ranges of the input parameters. The input includes the bedrock and surface-balance profiles along the flow line, some three-dimensional parameterization depending on the cross-section shape and the flow-line patterns, the flow properties of the ice, and a numerical basal lubrication factor.The movie shows how a number of different ice masses grow from zero thickness to either steady state or a periodically surging state depending on the input. Typical examples of real surging ice masses from the small to the large are closely matched by the model in many effects such as the period, duration, and speed of the surges, as well as the length and thickness changes.A preliminary study for the surging potential of a flow line in east Antarctica is also made even though the full temperature modelling is not included. The results indicate that periodic surging of the ice sheet can develop in spite of the expected high viscosity. The resultant surface profile is very similar to the measured profile. For much lower viscosities steady-state, fast-sliding, ice-stream flow develops.

scholarly journals A Movie Film Illustrating the Numerical Modelling of Periodically Surging Ice Masses

1976 ◽  
Vol 16 (74) ◽  
pp. 304-305
Author(s):  
W.F. Budd ◽  
B.J. Mcinnes
Keyword(s):  
Steady State ◽  
Flow Line ◽  
Three Dimensional ◽  
Surface Profile ◽  
High Viscosity ◽  
Ice Cap ◽  
Section Shape ◽  
Measured Profile ◽  
Full Temperature ◽  
Line Patterns

Abstract A general two-dimensional numerical model for a typical flow line of a glacier or ice cap has been developed which results in periodical surging for certain ranges of the input parameters. The input includes the bedrock and surface-balance profiles along the flow line, some three-dimensional parameterization depending on the cross-section shape and the flow-line patterns, the flow properties of the ice, and a numerical basal lubrication factor. The movie shows how a number of different ice masses grow from zero thickness to either steady state or a periodically surging state depending on the input. Typical examples of real surging ice masses from the small to the large are closely matched by the model in many effects such as the period, duration, and speed of the surges, as well as the length and thickness changes. A preliminary study for the surging potential of a flow line in east Antarctica is also made even though the full temperature modelling is not included. The results indicate that periodic surging of the ice sheet can develop in spite of the expected high viscosity. The resultant surface profile is very similar to the measured profile. For much lower viscosities steady-state, fast-sliding, ice-stream flow develops.

Changes in mass balance, velocity, and surface profile along a flow line on Barnes Ice Cap, 1970–1984

1987 ◽  
Vol 24 (8) ◽  
pp. 1550-1561 ◽  
Author(s):  
Roger LeB. Hooke ◽  
Gerald W. Johnson ◽  
Keith A. Brugger ◽  
Brian Hanson ◽  
Gerald Holdsworth
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
Surface Profile ◽  
Horizontal Velocity ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Transverse Strain ◽  
Average Mass ◽  
Ice Cap ◽  
Hydrostatic Approximation

On a number of occasions between 1970 and 1984, measurements of mass balance, surface velocity, and surface elevation were made along a 10.2 km flow line extending from the divide to the margin on Barnes Ice Cap, Baffin Island, Canada. The average mass balance rate on this Arctic ice cap appears to be controlled principally by summer temperature. Years of negative mass balance dominated during the 14 year period of the study; according to our measurements, this should have resulted in a thinning of an average of 2.65 m along the flow line. Surface-elevation measurements, however, suggest that the glacier thinned only ~ 1.7 m during this time period. The slightly compressive mean transverse strain can account for ~ 0.20 m of the discrepancy between these two figures. The rest is attributed to errors in mass balance. In particular, increases in density of old firn and freezing of water in crevasses could not be evaluated adequately from our measurements.The thinning was not uniform. Near the margin the glacier thinned ~ 5 m and near the divide, ~ 2.5 m, but between 3.5 and 5.5 km from the divide there seems to have been no substantial change in thickness. Thus, along the down-glacier half of the flow line the decrease in thickness was accompanied by an increase in slope.Within 4 km of the margin the decrease in thickness resulted in a decrease in horizontal velocity of up to ~ 15%, despite the increase in slope. Higher on the glacier, however, the horizontal velocity increased ~ 5%. These changes are broadly consistent with those estimated from the changes in shear stress calculated using the hydrostatic approximation.

scholarly journals Application of a Flow Model to the Ice-divide Region of Devon Island Ice Cap, Canada

1988 ◽  
Vol 34 (116) ◽  
pp. 55-63 ◽  
Author(s):  
N. Reeh ◽  
W.S.B. Paterson
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Vertical Velocity ◽  
Flow Model ◽  
Flow Line ◽  
Surface Strain ◽  
Ice Age ◽  
Depth Profiles ◽  
Devon Island ◽  
Ice Cap

AbstractThe steady-state flow model of Reeh (1988) is applied to a flow line that starts at the highest point of the Devon Island ice cap, follows the surface crest for 7.6 km, and then runs down the slope for a further 3.7 km. The effects of bedrock undulations, divergence of the flow lines, the variation of temperature with depth, and a basal layer of “soft” ice-age ice are taken into account. A flow law withn= 3 and a value ofAclose to that of Paterson (1981) is used. Longitudinal stress variations are neglected so that shear stress is calculated by the usual formula. It is estimated that these calculated values may be in error by at most 30%. Depth profiles of effective shear stress, and of the components of velocity and normal strain-rate, are presented at selected points along the flow line. These illustrate the large variations that occur near an ice divide and over bedrock undulations of amplitude comparable with the mean ice thickness. The model gives good predictions of the surface profile and of longitudinal and transverse surface strain-rates measured at ten points along the flow line. Predicted depth profiles of horizontal and vertical velocity components are compared with those measured in a bore hole. Comparison is limited by the fact that the model works in ice equivalent, whereas about 20% of the ice column consists of firn with different rheological properties from ice. The vertical velocity prediction is good. However, the model does not reproduce well the shape of the horizontal velocity profile, although measured and calculated fluxes differ only slightly. Predicted annual-layer thicknesses are within 15% of the measured ones in the upper half of the ice column, which consists of ice deposited in the last 1000 years. Predicted thicknesses in older ice are too small and the discrepancy increases with depth. This might indicate increased precipitation or, more likely, a thinner ice cap in the climatic optimum. However, it could also result from the fact that the layer of “soft” ice has been thinning continuously since the end of the ice age, so that the ice cap has never been in a steady state.

scholarly journals Abstracts of Papers Presented at the Symposium but not Published in Full in this Volume Computer: Modelling of Temperature Distributions in Polar Ice Sheets

1976 ◽  
Vol 16 (74) ◽  
pp. 293-294
Author(s):  
W.F. Budd ◽  
N.W. Young
Keyword(s):  
Steady State ◽  
Computer Modelling ◽  
Flow Line ◽  
Three Dimensional ◽  
Ice Cores ◽  
Surface Elevation ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Coupled Models ◽  
Dimensional Models

AbstractIt is now practicable to construct complete three-dimensional primitive- equation models of ice flow in which all the input may be time dependent. The input consists of bedrock and ocean distribution, accumulation net balance, ice-surface elevation- temperature relation, and the thermal and flow parameters of the ice. The main limitations on this type of model is the extensive demand of computation time. Thus simplified two-dimensional models have been developed for detailed flow-line studies, and single-column models have been used extensively for analysing the few deep bore-hole temperature profiles.The main feature of the measured temperature profiles reflect the current steady-state regime at each location. Deviations from the steady state are caused by time variations of any of the variables such as surface temperature, accumulation rate, ice thickness, velocity, etc.Measurements of stable-isotope ratios in the ice cores provide an indication of past temperatures which has been confirmed by the analysis of the temperature profiles. However the temperature changes could be either due to surface elevation changes or climate changes. Gas volumes in the core show promise of providing an indication of past elevations. Annual variations of the isotopes give indications of past accumulation rates. The determination of past velocities, however, requires velocity-temperature coupled models with more precise flow-law information.Three-dimensional models are necessary to study past variations of the flow-line pattern. Finally the sliding and surging models recently developed need to be incorporated into the cold ice-sheet models.

scholarly journals Abstracts of Papers Presented at the Symposium but not Published in Full in this Volume Computer: Modelling of Temperature Distributions in Polar Ice Sheets

1976 ◽  
Vol 16 (74) ◽  
pp. 293-294 ◽  
Author(s):  
W.F. Budd ◽  
N.W. Young
Keyword(s):  
Steady State ◽  
Computer Modelling ◽  
Flow Line ◽  
Three Dimensional ◽  
Ice Cores ◽  
Surface Elevation ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Coupled Models ◽  
Dimensional Models

Abstract It is now practicable to construct complete three-dimensional primitive- equation models of ice flow in which all the input may be time dependent. The input consists of bedrock and ocean distribution, accumulation net balance, ice-surface elevation- temperature relation, and the thermal and flow parameters of the ice. The main limitations on this type of model is the extensive demand of computation time. Thus simplified two-dimensional models have been developed for detailed flow-line studies, and single-column models have been used extensively for analysing the few deep bore-hole temperature profiles. The main feature of the measured temperature profiles reflect the current steady-state regime at each location. Deviations from the steady state are caused by time variations of any of the variables such as surface temperature, accumulation rate, ice thickness, velocity, etc. Measurements of stable-isotope ratios in the ice cores provide an indication of past temperatures which has been confirmed by the analysis of the temperature profiles. However the temperature changes could be either due to surface elevation changes or climate changes. Gas volumes in the core show promise of providing an indication of past elevations. Annual variations of the isotopes give indications of past accumulation rates. The determination of past velocities, however, requires velocity-temperature coupled models with more precise flow-law information. Three-dimensional models are necessary to study past variations of the flow-line pattern. Finally the sliding and surging models recently developed need to be incorporated into the cold ice-sheet models.

scholarly journals Application of a Flow Model to the Ice-divide Region of Devon Island Ice Cap, Canada

1988 ◽  
Vol 34 (116) ◽  
pp. 55-63 ◽  
Author(s):  
N. Reeh ◽  
W.S.B. Paterson
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Vertical Velocity ◽  
Flow Model ◽  
Flow Line ◽  
Surface Strain ◽  
Ice Age ◽  
Depth Profiles ◽  
Devon Island ◽  
Ice Cap

AbstractThe steady-state flow model of Reeh (1988) is applied to a flow line that starts at the highest point of the Devon Island ice cap, follows the surface crest for 7.6 km, and then runs down the slope for a further 3.7 km. The effects of bedrock undulations, divergence of the flow lines, the variation of temperature with depth, and a basal layer of “soft” ice-age ice are taken into account. A flow law with n = 3 and a value of A close to that of Paterson (1981) is used. Longitudinal stress variations are neglected so that shear stress is calculated by the usual formula. It is estimated that these calculated values may be in error by at most 30%. Depth profiles of effective shear stress, and of the components of velocity and normal strain-rate, are presented at selected points along the flow line. These illustrate the large variations that occur near an ice divide and over bedrock undulations of amplitude comparable with the mean ice thickness. The model gives good predictions of the surface profile and of longitudinal and transverse surface strain-rates measured at ten points along the flow line. Predicted depth profiles of horizontal and vertical velocity components are compared with those measured in a bore hole. Comparison is limited by the fact that the model works in ice equivalent, whereas about 20% of the ice column consists of firn with different rheological properties from ice. The vertical velocity prediction is good. However, the model does not reproduce well the shape of the horizontal velocity profile, although measured and calculated fluxes differ only slightly. Predicted annual-layer thicknesses are within 15% of the measured ones in the upper half of the ice column, which consists of ice deposited in the last 1000 years. Predicted thicknesses in older ice are too small and the discrepancy increases with depth. This might indicate increased precipitation or, more likely, a thinner ice cap in the climatic optimum. However, it could also result from the fact that the layer of “soft” ice has been thinning continuously since the end of the ice age, so that the ice cap has never been in a steady state.

scholarly journals 3D Printing of High Viscosity Reinforced Silicone Elastomers

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2239
Author(s):  
Nicholas Rodriguez ◽  
Samantha Ruelas ◽  
Jean-Baptiste Forien ◽  
Nikola Dudukovic ◽  
Josh DeOtte ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
New Technologies ◽  
Three Dimensional ◽  
High Viscosity ◽  
Layer By Layer ◽  
Silicone Elastomers ◽  
Uv Curable ◽  
Octet Truss ◽  
Tunable Mechanical Properties

Recent advances in additive manufacturing, specifically direct ink writing (DIW) and ink-jetting, have enabled the production of elastomeric silicone parts with deterministic control over the structure, shape, and mechanical properties. These new technologies offer rapid prototyping advantages and find applications in various fields, including biomedical devices, prosthetics, metamaterials, and soft robotics. Stereolithography (SLA) is a complementary approach with the ability to print with finer features and potentially higher throughput. However, all high-performance silicone elastomers are composites of polysiloxane networks reinforced with particulate filler, and consequently, silicone resins tend to have high viscosities (gel- or paste-like), which complicates or completely inhibits the layer-by-layer recoating process central to most SLA technologies. Herein, the design and build of a digital light projection SLA printer suitable for handling high-viscosity resins is demonstrated. Further, a series of UV-curable silicone resins with thiol-ene crosslinking and reinforced by a combination of fumed silica and MQ resins are also described. The resulting silicone elastomers are shown to have tunable mechanical properties, with 100–350% elongation and ultimate tensile strength from 1 to 2.5 MPa. Three-dimensional printed features of 0.4 mm were achieved, and complexity is demonstrated by octet-truss lattices that display negative stiffness.

scholarly journals The first observation of 4D tomography measurement of plasma structures and fluctuations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chanho Moon ◽  
Kotaro Yamasaki ◽  
Yoshihiko Nagashima ◽  
Shigeru Inagaki ◽  
Takeshi Ido ◽  
...  
Keyword(s):  
Steady State ◽  
Three Dimensional ◽  
Axial Direction ◽  
Axial Position ◽  
Entire Cross Section ◽  
Helicon Plasma ◽  
Emission Profile ◽  
Dimensional Measurement ◽  
Tomography System ◽  
Three Dimensional Measurement

AbstractA tomography system is installed as one of the diagnostics of new age to examine the three-dimensional characteristics of structure and dynamics including fluctuations of a linear magnetized helicon plasma. The system is composed of three sets of tomography components located at different axial positions. Each tomography component can measure the two-dimensional emission profile over the entire cross-section of plasma at different axial positions in a sufficient temporal scale to detect the fluctuations. The four-dimensional measurement including time and space successfully obtains the following three results that have never been found without three-dimensional measurement: (1) in the production phase, the plasma front propagates from the antenna toward the end plate with an ion acoustic velocity. (2) In the steady state, the plasma emission profile is inhomogeneous, and decreases along the axial direction in the presence of the azimuthal asymmetry. Furthermore, (3) in the steady state, the fluctuations should originate from a particular axial position located downward from the helicon antenna.

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