A Discrete Element Model to Study Marginal Ice Zone Dynamics and the Behaviour of Vessels Moored in Broken Ice PDF Download

Author: Edmond Hansen
Publisher:
ISBN: 9788247103418
Category :
Languages : en
Pages : 159

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Author: H. Konietzky
Publisher: Routledge
ISBN: 135142758X
Category : Technology & Engineering
Languages : en
Pages : 334

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Particle methods have seen increasing use in several engineering and scientific fields, both because of their unique modelling capabilities and the availability of the necessary computational power. This title focuses on their theory and application.

Author: Sirpa Häkkinen
Publisher:
ISBN:
Category : Ocean-atmosphere interaction
Languages : en
Pages : 124

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This study is aimed at the modelling of mesoscale processes such as up/downwelling and ice edge eddies in the marginal ice zones. A 2-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model (f-plane) through interfacial stresses. The constitutive equations of the sea ice are formulated on the basis of the Reiner-Rivlin theory. The internal ice stresses are important only at high ice concentrations (90-100%), otherwise the ice motion is essentially free drift, where the air-ice stress is balanced by the ice-water stress. The model was tested by studying the upwelling dynamics. Winds parallel to the ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux, and thus the Ekman transport is bigger under the ice than in the open water. The upwelling simulation was extended to include temporally varying forcing, which was chosen to vary sinusoidally with 4 day period. This forcing resembles successive cyclone passings. In the model with thin oceanic upper layer, ice bands were formed. The up/downwelling signals do not disappear in wind reversals because of nonlinear advection. This leads to convergences and divergences in oceanic and ice velocities which manifest themselves as ice banding. At least one wind reversal is needed to produce one ice band.

Author: Matti Leppaeranta
Publisher:
ISBN:
Category :
Languages : en
Pages : 10

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Most of the work this year was involved with processing the data of MIZEX-83 and MIZEX-84 experiments in the Greenland Sea. MIZEX-83 was a pilot study program where ice kinematics data could be collected for about ten days. (see Fourth Interim Report). Ocean current measurements were made simultaneously by the Univ. of Bergen, and they had three stations in the same ice floes as we had transponders for the ice kinematics study. MIZEX-84 was the main summer experiment of the MIZEX program. Iced kinematics data was collected for forty days from R/V Polarqueen, which was the main drifting station. A manuscript was prepared on one-dimensional modeling studies of ice drift in the marginal ice drift in the marginal ice zone.

Author: Jie Dai
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This thesis investigates the numerical modelling of Dynamic Position (DP) in pack ice. A two-dimensional numerical model for ship-ice interaction was developed using the Discrete Element Method (DEM). A viscous-elastic ice rheology was adopted to model the dynamic behaviour of the ice floes. Both the ship-ice and the ice-ice contacts were considered in the interaction force. The environment forces and the hydrodynamic forces were calculated by empirical formulas. After the current position and external forces were calculated, a Proportional-Integral-Derivative (PID) control and thrust allocation algorithms were applied on the vessel to control its motion and heading. The numerical model was coded in Fortran 90 and validated by comparing computation results to published data. Validation work was first carried out for the ship-ice interaction calculation, and former researchers' simulation and model test results were used for the comparison. With confidence in the interaction model, case studies were conducted to predict the DP capability of a sample Arctic DP vessel.

Author: Karl Patrick Lawrence
Publisher:
ISBN:
Category :
Languages : en
Pages : 329

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This thesis is composed of theoretical, experimental, and numerical studies. In Part I, it discusses fundamental challenges of the discrete element method, provides a set of algorithms for addressing them, and presents performance gains of an improved algorithm on a target computer platform. A new contact detection and force resolution algorithm based upon (i) the fast common-plane (FCP) algorithm, (ii) using axisaligned bounding boxes (AABBs) to perform a proximity search, (iii) estimating the time of collision, and (iv) accurate resolution of contact points is presented. Benchmark simulations indicate an order of magnitude increase in performance is achievable for a relatively small number of elements. A new parallel discrete element algorithm is presented which combines the domain decomposition, object-oriented, and perfectly parallel strategies of parallelism to eliminate the drawbacks of parallel discrete element algorithms put forth by past studies. A significant speed-up is observed in comparison to past studies in trials conducted on a NUMA-based SMP computer. In Part II, various applications of the discrete element method are reviewed, with an emphasis on ice-structure interaction. The conical design of the Kulluk drillship is of particular interest due to its success in operating in the Beaufort Sea from 1975- 1993 and its subsequent purchase and recommission by Shell in 2006. Three previous experimental studies and a unique set of full-scale data measurements form the basis for comparison of a concurrent experimental and numerical investigation. The results of a model scale experiment at the NRC-IOT are analyzed and presented, followed by results of the numerical simulations. A 1:40 scale replica of the Kulluk platform in level ice produces results which are consistent with past experiments and confirm expected trends as well as different regimes of results dependent on the ductile/brittle behavior of ice. The numerical setup models the full-scale platform in three dimensions with a 24-sided rigid conical structure, ice as an elastic brittle material with plate-bending elements, and platform mooring through the implementation of a spread mooring algorithm. Numerical results are in agreement with past results for ice thickness of less than 1.2m, confirming that the initial design goal of the Kulluk was achieved while still overestimating the loads in comparison to the full-scale data set. Two explanations are presented for the non-conformity of the experimental and numerical predictions to the full-scale data results.

Author: Michael Steele
Publisher:
ISBN:
Category :
Languages : en
Pages : 203

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Author: Anton Kulchitsky
Publisher:
ISBN:
Category : Discrete element method
Languages : en
Pages : 40

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Author: W. D. Hibler (III.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 104

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Book Description
The main goal of the marginal ice zone experiment (MIZEX) is to understand the processes that dictate the advance and retreat of the ice margin. Mechanistic model sensitivity studies can greatly aid in this goal by identifying the relative importance of different processes in the total system. In addition, more complete simulation models can be used both to test the adequacy of current understanding of the marginal ice zone and to serve as an integrating device for complex data sets. This volume contains the main results from a MIZEX modeling workshop held 18-20 October in Hanover, New Hampshire. Modelers interested in both Arctic and Antarctic sea ice were present. The purpose of the workshop was to determine the status of marginal ice zone modeling and to discuss different views on modeling processes in the MIZ. Results from full simulation models, mechanistic models, and empirical statistical models were presented and discussed. In addition, recommendations relevant to experimental measurements were made. The recommendations were divided into ocean, ice, and atmospheric categories; these were also the three main subject areas covered by the presentations. Overall, the workshop helped to identify areas where further simulations are needed to test our understanding and where knowledge of certain processes is lacking.

Author: Ryszard Staroszczyk
Publisher: Springer
ISBN: 9783030030377
Category : Science
Languages : en
Pages : 0

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This book presents the concepts and tools of ice mechanics, together with examples of their application in the fields of glaciology, climate research and civil engineering in cold regions. It starts with an account of the most important physical properties of sea and polar ice treated as an anisotropic polycrystalline material, and reviews relevant field observations and experimental measurements. The book focuses on theoretical descriptions of the material behaviour of ice in different stress, deformation and deformation-rate regimes on spatial scales ranging from single ice crystals, those typical in civil engineering applications, up to scales of thousands of kilometres, characteristic of large, grounded polar ice caps in Antarctica and Greenland. In addition, it offers a range of numerical formulations based on either discrete (finite-element, finite-difference and smoothed particle hydrodynamics) methods or asymptotic expansion methods, which have been used by geophysicists, theoretical glaciologists and civil engineers to simulate the behaviour of ice in a number of problems of importance to glaciology and civil engineering, and discusses the results of these simulations. The book is intended for scientists, engineers and graduate students interested in mathematical and numerical modelling of a wide variety of geophysical and civil engineering problems involving natural ice.