scholarly journals Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams

2014 ◽  
Vol 8 (6) ◽  
pp. 2007-2029 ◽  
Author(s):  
J. Thompson ◽  
M. Simons ◽  
V. C. Tsai
Keyword(s):  
Three Dimensional ◽  
Hydrologic Model ◽  
Ice Streams ◽  
Ice Stream ◽  
Nonlinear Viscoelastic ◽  
Grounding Line ◽  
Dimensional Finite Element ◽  
Order Of Magnitude ◽  
Three Dimensional Finite Element ◽  
The Impact

Abstract. Geodetic surveys suggest that ocean tides can modulate the motion of Antarctic ice streams, even at stations many tens of kilometers inland from the grounding line. These surveys suggest that ocean tidal stresses can perturb ice stream motion at distances about an order of magnitude farther inland than tidal flexure of the ice stream alone. Recent models exploring the role of tidal perturbations in basal shear stress are primarily one- or two-dimensional, with the impact of the ice stream margins either ignored or parameterized. Here, we use two- and three-dimensional finite-element modeling to investigate transmission of tidal stresses in ice streams and the impact of considering more realistic, three-dimensional ice stream geometries. Using Rutford Ice Stream as a real-world comparison, we demonstrate that the assumption that elastic tidal stresses in ice streams propagate large distances inland fails for channelized glaciers due to an intrinsic, exponential decay in the stress caused by resistance at the ice stream margins. This behavior is independent of basal conditions beneath the ice stream and cannot be fit to observations using either elastic or nonlinear viscoelastic rheologies without nearly complete decoupling of the ice stream from its lateral margins. Our results suggest that a mechanism external to the ice stream is necessary to explain the tidal modulation of stresses far upstream of the grounding line for narrow ice streams. We propose a hydrologic model based on time-dependent variability in till strength to explain transmission of tidal stresses inland of the grounding line. This conceptual model can reproduce observations from Rutford Ice Stream.

scholarly journals Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams

2014 ◽  
Vol 8 (2) ◽  
pp. 2119-2177 ◽  
Author(s):  
J. Thompson ◽  
M. Simons ◽  
V. C. Tsai
Keyword(s):  
Three Dimensional ◽  
Hydrologic Model ◽  
Ocean Tides ◽  
Ice Streams ◽  
Ice Stream ◽  
Nonlinear Viscoelastic ◽  
Grounding Line ◽  
Order Of Magnitude ◽  
Three Dimensional Finite Element ◽  
The Impact

Abstract. Geodetic surveys suggest that ocean tides can modulate the motion of Antarctic ice streams. Data from Whillans Ice Plain, Rutford Ice Stream, and other Antarctic ice streams show periodicity in flow velocity at periods similar to those of ocean tides at geodetic stations many tens of kilometers inland from the grounding line. These data suggest that ocean tidal stresses can perturb ice stream motion at distances about an order of magnitude farther inland than tidal flexure of the ice stream alone. Recent models exploring the role of tidal perturbations in basal shear stress are primarily two-dimensional, with the impact of the ice stream margins either ignored or parameterized. Here, we use two- and three-dimensional finite element modeling to investigate transmission of tidal stresses in ice streams and the impact of considering more realistic, three-dimensional ice stream geometries. Using Rutford Ice Stream as a real-world comparison, we demonstrate that the assumption that elastic tidal stresses in ice streams propagate large distances inland fails for channelized glaciers due to an intrinsic, exponential decay in the stress due to resistance at the ice stream margins. This behavior is independent of basal conditions beneath the ice stream and cannot be fit to observations using either elastic or nonlinear viscoelastic rheologies without nearly complete decoupling of the ice stream from its lateral margins. Our results suggest that a mechanism external to the ice stream is necessary to explain the tidal modulation of stresses far upstream of the grounding line for narrow ice streams. We propose a hydrologic model based on time-dependent variability in till strength to explain transmission of tidal stresses inland of the grounding line. This conceptual model reproduces observations from Rutford Ice Stream.

scholarly journals Focality of the Induced E-Field Is a Contributing Factor in the Choice of TMS Parameters: Evidence from a 3D Computational Model of the Human Brain

2020 ◽  
Vol 10 (12) ◽  
pp. 1010
Author(s):  
Deepika Konakanchi ◽  
Amy L. de Jongh Curry ◽  
Robert S. Waters ◽  
Shalini Narayana
Keyword(s):  
Spatial Distribution ◽  
Three Dimensional ◽  
Fem Simulation ◽  
Element Model ◽  
Brain Areas ◽  
Invasive Approach ◽  
Non Invasive ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
The Impact

Transcranial magnetic stimulation (TMS) is a promising, non-invasive approach in the diagnosis and treatment of several neurological conditions. However, the specific results in the cortex of the magnitude and spatial distribution of the secondary electrical field (E-field) resulting from TMS at different stimulation sites/orientations and varied TMS parameters are not clearly understood. The objective of this study is to identify the impact of TMS stimulation site and coil orientation on the induced E-field, including spatial distribution and the volume of activation in the cortex across brain areas, and hence demonstrate the need for customized optimization, using a three-dimensional finite element model (FEM). A considerable difference was noted in E-field values and distribution at different brain areas. We observed that the volume of activated cortex varied from 3000 to 7000 mm3 between the selected nine clinically relevant coil locations. Coil orientation also changed the induced E-field by a maximum of 10%, and we noted the least optimal values at the standard coil orientation pointing to the nose. The volume of gray matter activated varied by 10% on average between stimulation sites in homologous brain areas in the two hemispheres of the brain. This FEM simulation model clearly demonstrates the importance of TMS parameters for optimal results in clinically relevant brain areas. The results show that TMS parameters cannot be interchangeably used between individuals, hemispheres, and brain areas. The focality of the TMS induced E-field along with its optimal magnitude should be considered as critical TMS parameters that should be individually optimized.

Numerical Simulation of Inclined Multi-Seam Mining Subsidence of Considered the Impact by Faults

2011 ◽  
Vol 250-253 ◽  
pp. 2135-2140
Author(s):  
Zhi Ping Wu ◽  
Sheng Hua Qiu ◽  
Ying Li
Keyword(s):  
Working Conditions ◽  
Three Dimensional ◽  
Surface Subsidence ◽  
Differential Settlement ◽  
Geological Condition ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Seam Mining ◽  
The Impact ◽  
Roof Strata

According to the complex mining geological condition of Shandong gentle inclined multi-seam mining, Use the three-dimensional finite element numerical analysis software to establish three-dimensional geological model under the different mining working conditions. Taking into account the impact of faults to calculate multi-seam roof strata movement and surface subsidence caused by the different mining working conditions. The level displacement & subsidence distribution curve of the reference point of surface & multi-seam roof strata under the different working conditions is shown. The maximum, minimum settlement, differential settlement and subsidence diagram is shown. And the principal stress, shear stress value of surface & multi-seam roof strata after mining also is shown. The results showed that: little change of the biggest surface subsidence and differential settlement is caused by mining 3101&3102 face or separate 3101 or 3102 face. And the largest subsidence, and the settlement difference of the surface is 520mm, 498mm, 515mm and 59mm, 78mm, 81mm, Respectively. It provides an reference for reasonable, safe, economic for the inclined multi-seam mining under similar conditions.

Prediction of the yielding behaviour of ductile porous materials through computational homogenization

2018 ◽  
Vol 35 (2) ◽  
pp. 604-621
Author(s):  
Rodrigo Pinto Carvalho ◽  
Igor A. Rodrigues Lopes ◽  
Francisco M. Andrade Pires
Keyword(s):  
Three Dimensional ◽  
Yield Locus ◽  
Analytical Models ◽  
Finite Element Models ◽  
Content Type ◽  
Ductile Materials ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Void Geometry ◽  
The Impact

Purpose The purpose of this paper is to predict the yield locus of porous ductile materials, evaluate the impact of void geometry and compare the computational results with existing analytical models. Design/methodology/approach A computational homogenization strategy for the definition of the elasto-plastic transition is proposed. Representative volume elements (RVEs) containing single-centred ellipsoidal voids are analysed using three-dimensional finite element models under the geometrically non-linear hypothesis of finite strains. Yield curves are obtained by means of systematic analysis of RVEs considering different kinematical models: linear boundary displacements (upper bound), boundary displacement fluctuation periodicity and uniform boundary traction (lower bound). Findings The influence of void geometry is captured and the reduction in the material strength is observed. Analytical models usually overestimate the impact of void geometry on the yield locus. Originality/value This paper proposes an alternative criterion for porous ductile materials and assesses the accuracy of analytical models through the simulation of three-dimensional finite element models under geometrically non-linear hypothesis.

Optimization of the Engine Hood to Reduce the Head Injury during the Vehicle-Human Collision

2012 ◽  
Vol 192 ◽  
pp. 29-36
Author(s):  
Yu Xin Wang ◽  
Qing Chun Wang ◽  
Jian Rong Fu ◽  
Hong Hai Qiao
Keyword(s):  
Finite Element ◽  
Head Injury ◽  
Optimization Design ◽  
Three Dimensional ◽  
Element Model ◽  
Head Model ◽  
Modeling Software ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
The Impact

Effect of hard point of the engine hood on the head injury during the vehicle-human collision was studied to improve the design of engine hood. Firstly, the current common model of the engine hood was established with three-dimensional finite element modeling software, and 20 areas were divided, also a standard head finite element model was imported, secondly, each area of the engine hood was clashed by the standard head model, then the impact on the head injure was analyzed and the hard point of the hood area was achieved, thirdly, the optimization of the inside and outside panel materials and the plate structure were carried out to reduce the head damage. The simulation results show that the engine hood after optimization gave less damage to the head, which means the research carried out here is of a good reference to the engine hood optimization design for human protection

A Study on Motions and Connector Loads for a New Type of Two-Module Semi-Submersible

2019 ◽  
Author(s):  
Jun Ding ◽  
Chao Tian ◽  
Yuji Miao ◽  
Zhengwei Zhang ◽  
Zhanhua Zhao ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Short Term ◽  
Term Forecast ◽  
Dimensional Finite Element ◽  
Order Of Magnitude ◽  
New Type ◽  
The Subject ◽  
Three Dimensional Finite Element ◽  
Marine Platform

Abstract The hydrodynamic model and three-dimensional finite element model of a new type of two-module marine platform were built for the subject of research. The motions and connector loads were predicted based on the COMPASS THAFTS software and the results were in agreement with the model tests. It shows that the new type platform has a good sea keeping performance. On the other hand, the short-term forecast results indicate that the connector loads, Fz, is larger than other two directions, approaching 200t. The connector loads, Fx and Fy, are usually in the order of magnitude of tens tons. Some useful conclusions obtained in this paper can provide an important reference for the optimal design and construction of the new type platform and its connector system.

Fire Durations of Concern for a Modern Legal Weight Truck Cask

2006 ◽  
Author(s):  
Neelima Mallidi ◽  
Miles Greiner ◽  
Venkata V. R. Venigalla
Keyword(s):  
Thermal Protection ◽  
Three Dimensional ◽  
Time History ◽  
Element Analysis ◽  
Pressurized Water ◽  
Dimensional Finite Element ◽  
Term Creep ◽  
Three Dimensional Finite Element ◽  
The Impact ◽  
Containment Integrity

The response of a truck package designed to transport four pressurized water reactor fuel assemblies to a simplified radiation fire model is simulated for a range of fire durations using three-dimensional finite element analysis. A model is developed to determine the cumulative seal degradation from its temperature versus time history. This model is used to determine the minimum fire duration that causes the seal to lose containment integrity. The fire durations that cause the maximum cladding temperature to reach its long term creep deformation and burst rupture temperatures are determined and found to be longer than the duration that cause the seal to lose containment integrity. These simulations are repeated for package models without the compliant regions of the impact limiters, and for a package with the impact limiter completely removed. These simulations quantify the level of thermal protection the impact limiters provide to the seals and cladding during simulated fires.

Effect of Fins on Combined Loaded Suction Caisson in Deepwater Clay Soils. A Numerical Analysis

2021 ◽  
Author(s):  
Pablo Castillo Garcia ◽  
Stylianos Panayides
Keyword(s):  
Soft Clay ◽  
Three Dimensional ◽  
Cost Savings ◽  
Clay Soils ◽  
Suction Caisson ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
In The Beginning ◽  
The Impact ◽  
Fin Length

Abstract Suction piles are a form of foundation widely adopted in the offshore energy industry. Efforts to enhance the combined Vertical-Horizontal (V-H) performance of piles with the addition of fins, attracted interest from the engineering community in the beginning of the 21st century. Design of this enhancement was surfaced whilst examining foundation solutions for renewable energy projects. Studies to date have primarly considered relatively shallow waters comprising sandy soils, with the behaviour of fin-enhanced piles in very soft to soft clay soils, receiving less attention. The present study emphasis is on typical deep-water deposits of soft clay and attempts to evaluate the impact of varying fin length, shape, orientation and location, on the combined capacity of suction piles by means of three-dimensional finite element analyses. The paper investigates two types of load configuration; in the first instance loading at the pile head and secondly with the load attachment point located at approximately two thirds of the pile embedded length. These two configurations cover different foundation solutions, such as support for subsea infrastructure and anchoring for floating facilities, respectively. Optimum fin-enhanced suction pile configurations are presented for each application, with the results from this study indicating an increase of the load-carrying capacity in V-H space, whilst reducing the overall suction pile size. The efficiency of various configurations is presented with composite plots of increase in holding capacity, plotted against the increase in steel surface area. Preliminary recommendations on fin length, location, shape and orientation for typical suction pile applications are presented with intent to demonstrate the potential for cost savings and reduction in both operational and schedule risk.

scholarly journals Three-dimensional modelling of the dynamics of Johnsons Glacier, Livingston Island, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 1-8 ◽  
Author(s):  
Carlos Martín ◽  
Francisco Navarro ◽  
Jaime Otero ◽  
María L. Cuadrado ◽  
María I. Corcuera
Keyword(s):  
Water Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Glacier System ◽  
Ice Surface ◽  
Glacier Terminus ◽  
Livingston Island ◽  
Dimensional Finite Element ◽  
Order Of Magnitude ◽  
Three Dimensional Finite Element

AbstractA new three-dimensional finite-element model of the steady-state dynamics of temperate glaciers has been developed and applied to Johnsons Glacier, Livingston Island, Antarctica, with the aim of determining the velocity and stress fields for the present glacier configuration. It solves the full Stokes system of differential equations without recourse to simplifications such as those involved in the shallow-ice approximation. Rather high values of the stiffness parameter B (∼0.19–0.23MPaa1/3) are needed to match the observed ice surface velocities, although these results do not differ much from those found by other authors for temperate glaciers. Best-fit values of the coefficient k in the sliding law (*2.2–2.7 x 103m a–1MPa–2) are also of the same order of magnitude as those found by other authors. The results for velocities are satisfactory, though locally there exist significant discrepancies between computed and observed ice surface velocities, particularly for the vertical ones. This could be due to failures in the sliding law (in particular, the lack of information on water pressure), the use of an artificial down-edge boundary condition and the fact that bed deformation is not considered. For the whole glacier system, the driving stress is largely balanced by the basal drag (80% of the driving stress). Longitudinal stress gradients are only important in the divide areas and near the glacier terminus, while lateral drag is only important at both sides of the terminal zone.

Impact of Self-Assembly Process Errors on Thermoelectric Performance

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Nathan B. Crane ◽  
Patrick McKnight
Keyword(s):  
Self Assembly ◽  
High Performance ◽  
Three Dimensional ◽  
Assembly Process ◽  
Thermoelectric Devices ◽  
One Dimensional ◽  
Assembly Accuracy ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
The Impact

Thermoelectric devices have many scaling benefits that motivate miniaturization, but assembly of small components is a significant challenge. Self-assembly provides a promising method for integrating very small elements. However, it introduces the possibility of stochastic errors with significant performance impacts. This work presents a method to estimate the impact of these errors on system performance. Equivalent thermoelectric properties are developed that adjust for the effect of missing elements in one-dimensional thermoelectric models. The models show that the thermoelectric devices can accommodate significant self-assembly errors by incorporation of redundant electrical paths. The model shows nearly linear decline in effective power factor with declining assembly accuracy, but the effective figure of merit (ZT) is relatively insensitive to assembly errors. Predictions from the modified one-dimensional model agree well with three-dimensional finite element simulations. This work identifies two basic strategies for how devices such as thermoelectric could be designed for self-assembly and demonstrates that it is possible to achieve high performance despite self-assembly process errors.

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