scholarly journals A review of level ice and brash ice growth models

2021 ◽  
pp. 1-20
Author(s):  
Vasiola Zhaka ◽  
Robert Bridges ◽  
Kaj Riska ◽  
Andrzej Cwirzen
Keyword(s):  
Meteorological Parameters ◽  
Growth Models ◽  
Winter Season ◽  
Consolidation Process ◽  
Ice Growth ◽  
Ice Accumulation ◽  
Forecast Models ◽  
Ice Conditions ◽  
Level Ice ◽  
Breaking Cycles

Abstract Brash ice forms in harbours and ship channels from frequent ship passages and the resulting freezing–breaking cycles create a unique ice formation. The brash ice accumulation over the winter season is a result of meteorological, thermodynamical and mechanical processes. A reliable brash ice growth model is an important asset when determining navigation routes through ice conditions and when establishing port ice management solutions. This review aims to describe the brash ice development and its modelling as well as the key parameters that influence the brash ice growth and its estimation. This paper summarises the brash ice growth models and the fundamental theories of level ice growth upon which these models are based, and outlines the main knowledge gaps. The results highlight the importance of porosity and piece size distribution and their effect on the consolidation process. The inclusion of the brash ice lateral movement and the side ridge formation would improve the accuracy of forecast models. Furthermore, the findings of the study identify the effect of omitting meteorological parameters such as snow and radiation, from the brash ice growth models. Their contribution to the level ice thickness suggests a significant influence on the brash ice consolidation process.

Model Tests on a Spar in Level Ice and Ice Ridge Conditions

2009 ◽  
Author(s):  
John Murray ◽  
Stephane LeGuennec ◽  
Don Spencer ◽  
Chang K. Yang ◽  
Wooseuk Yang
Keyword(s):  
Full Scale ◽  
Scale Model ◽  
Test Facility ◽  
Mooring System ◽  
Scaling Effects ◽  
Line System ◽  
Restoring Forces ◽  
Ice Conditions ◽  
Ice Loads ◽  
Level Ice

1:30 and 1:50 model-scale ice tests of an ice-resistant Spar design were carried out to determine the loads on the Spar in level ice and ice ridges. Due to limitations in the depth of the ice test facility, the hull draft and mooring system were truncated. The 1:30 scale model was towed through the ice on a fixed and compliant dynamometer. The stiffness characteristics of the compliant dynamometer matched the horizontal stiffness of the full-scale mooring system. The purpose of these tests was to compare the mooring and ice loads measured in fixed and compliant conditions. The 1:50 scale model was truncated by 70 m. Its mooring system was modeled using a four-line system designed to give the same global restoring forces as the full-scale mooring system. The model was fitted with vertical plates on the exterior of the hull to compensate for loss of added mass and added moment of inertia. A limited number of tests were carried out at the two model scales in the same ice conditions to investigate scaling effects. The mooring and ice loads measured in the fixed and compliant conditions were found to be similar, indicating that loads estimated, assuming the structure is fixed, provide good estimates. Good agreement between the two models was also found for the tests carried out in the same ice conditions, suggesting that the scaling effects may be negligible.

scholarly journals Performance of a multiscale correlation algorithm for the estimation of sea-ice drift from SAR images: initial results

2011 ◽  
Vol 52 (57) ◽  
pp. 311-317 ◽  
Author(s):  
Thomas Hollands ◽  
Wolfgang Dierking
Keyword(s):  
Sea Ice ◽  
Displacement Vector ◽  
Winter Season ◽  
Image Resolution ◽  
Displacement Fields ◽  
Sar Images ◽  
High Entropy ◽  
Ice Drift ◽  
Sea Ice Drift ◽  
Ice Conditions

AbstractSea-ice drift fields were obtained from sequences of synthetic aperture radar (SAR) images using a method based on pattern recognition. the accuracy of the method was estimated for two image products of the Envisat Advanced SAR (ASAR) with 25 m and 150 m pixel size. For data from the winter season it was found that 99% of the south–north and west–east components of the determined displacement vector are within ±3–5 pixels of a manually derived reference dataset, independent of the image resolution. For an image pair with 25 m resolution acquired during summer, the corresponding value is 12 pixels. Using the same resolution cell dimensions for the displacement fields in both image types, the estimated displacement components differed by 150–300 m. the use of different texture parameters for predicting the performance of the algorithm dependent on ice conditions and image characteristics was studied. It was found that high entropy values indicate a good performance.

Ice Model Testing of Structures With a Downward Breaking Cone at the Waterline JIP: Presentation, Set-Up and Objectives

2011 ◽  
Author(s):  
Per Kristian Bruun ◽  
Sveinung Lo̸set ◽  
Arne Gu¨rtner ◽  
Guido Kuiper ◽  
Ted Kokkinis ◽  
...  
Keyword(s):  
First Year ◽  
Test Set ◽  
Ice Load ◽  
Fixed Model ◽  
Ice Conditions ◽  
Level Ice ◽  
Ice Model Test ◽  
Set Up ◽  
Ice Failure ◽  
Ice Model

Two large ice model test campaigns were performed in the period 2007–2010 as a part of a Joint Industry Project. The objectives of the project were to investigate different floater geometries and ice model test set-ups (model fixed to a carriage and pushed through the ice vs. ice pushed towards a floating model moored to the basin bottom) and their influence on the ice failure mode and structure responses in the various tested ice conditions. This paper presents the objectives and motivations for the project, the models tested, the target test set-up for the various tested configurations and the test matrix. Initial results from a fixed model tested in three first-year ice ridges with similar target ice properties are also presented and compared. Fixed models of both deep and shallow water platforms were tested in various ice conditions. All models except one had a downward breaking cone at the waterline. The influences of the waterline diameter, the angle of the downward breaking cone and the vertical cone height on the ice failure mode and the resulting ice load were investigated. Tests were conducted in level ice with a thickness ranging from 2 to 3 m and variable ice drift speeds ranging from 0.1 to 1.0 m/s in full scale values. The models were subjected to tests in managed level ice with varying speeds, ice concentrations and ice floe sizes. Fixed structures were also subjected to testing in typical first-year design ice ridge conditions with ridges of different depths and widths, as well as one multi-year ice ridge. One fixed model was also utilised for testing of the repeatability of scaled ice model testing. Moored models with the same waterline geometry as the fixed models were also tested. The moored models were tested in ice conditions similar to those of the fixed models with the objective of comparing their influences on the ice load due to structural responses.

Experimental and Numerical Investigation of Dynamic Positioning in Level Ice

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Ivan Metrikin ◽  
Sofien Kerkeni ◽  
Peter Jochmann ◽  
Sveinung Løset
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Positioning ◽  
Public And Private ◽  
The Public ◽  
Six Degrees Of Freedom ◽  
Deep Waters ◽  
Ice Conditions ◽  
Level Ice ◽  
Ice Floes ◽  
Novel Model

Offshore operations in ice-covered waters are drawing considerable interest from both the public and private sectors. Such operations may require vessels to keep position during various activities, such as lifting, installation, crew change, evacuation, and possibly drilling. In deep waters, mooring solutions become uneconomical and, therefore, dynamic positioning (DP) systems are attractive. However, global loads from drifting sea ice can be challenging for stationkeeping operations of DP vessels. To address this challenge, the current paper investigates DP in level ice conditions using experimental and numerical approaches. The experimental part describes a set of ice model tests which were performed at the large ice tank of the Hamburg Ship Model Basin (HSVA) in the summer and autumn of 2012. Experimental design, instrumentation, methods, and results are presented and discussed. The numerical part presents a novel model for simulating DP operations in level ice, which treats both the vessel and the ice floes as separate independent bodies with six degrees-of-freedom. The fracture of level ice is calculated on-the-fly based on numerical solution of the ice material failure equations, i.e., the breaking patterns of the ice are not precalculated. The numerical model is connected to a DP controller and the two systems interchange data dynamically and work in a closed-loop. The structures of the models, as well as the physical and mathematical assumptions, are discussed in the paper. Finally, several ice basin experiments are reproduced in the numerical simulator, and the results of the physical and numerical tests are compared and discussed.

Ice Tank Testing of a Surface Buoy for Arctic Conditions

2008 ◽  
Author(s):  
Oddgeir Dalane ◽  
Ove Tobias Gudmestad ◽  
Sveinung Lo̸set ◽  
Jo̸rgen Amdahl ◽  
Tor Erik Hilde`n ◽  
...  
Keyword(s):  
Test Results ◽  
Floating Structures ◽  
Deep Waters ◽  
Ice Drift ◽  
Arctic Conditions ◽  
Ice Conditions ◽  
Level Ice ◽  
Ridged Ice ◽  
Ice Forces ◽  
Multiyear Ice

A moored Shallow Draught Buoy (SDB) for potential operations in Arctic waters was tested during the summer of 2006 in the model laboratory basin at the Hamburg Ship Model Basin (HSVA) in Hamburg. The conceptual design of this buoy was based on the design of the Kulluk exploration vessel which operated in the Beaufort Sea in the 1980’s and early 1990’s. The concept was tested in ice conditions representing level ice, multiyear ice and ridged ice, where the ice thickness, ice drift velocity and flexural strength were varied in the different test runs. Moored structures are believed to be favourable in deep waters with ice present, but there exist insufficient information and data about the actions on and behaviour of moored floating structures in ice to support this. The purpose of the present paper is to evaluate the model test results and look at the dynamic ice loading and response of the structure. The ice forces on the structure were calculated from the structure’s response and response power density spectra were used to evaluate the periodic forces and displacements. Based on the analysis of the test data, an increased understanding of the behaviour of the surface buoy is presented.

Subsurface Ice Transport at a Transversally Towed Ship Model

2017 ◽  
Author(s):  
Li Zhou ◽  
Rüdiger U. Franz von Bock und Polach ◽  
Xu Bai
Keyword(s):  
Froude Number ◽  
Densimetric Froude Number ◽  
Ship Model ◽  
Drift Speed ◽  
Ice Accumulation ◽  
Underwater Cameras ◽  
Low Froude Number ◽  
Broken Ice ◽  
Level Ice ◽  
Ice Floes

The subsurface transport of ice along the underwater body of a ship hull or a structure may cause damages to appendages. In order to investigate the conditions under which the ice accumulation occurs, a series of model tests was carried out in the ice basin of Aalto University. The used ship model was towed laterally against the ice with one side breaking level ice. The transport of broken ice floes broken off from the intact ice sheet has been has been monitored with underwater cameras. Both the model drift speed, respectively the ice drift speed, and the ice thickness are found to affect ice accumulation process. The Densimetric Froude number is introduced as measured to determine whether ice floes will accumulate on the upstream of the hull. It is found that ice accumulation is triggered at relatively low Froude number.

scholarly journals Formation and movement of ice accumulation waves under ice cover –an experimental study

2019 ◽  
Vol 67 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Jun Wang ◽  
Yifan Wu ◽  
Jueyi Sui ◽  
Bryan Karney
Keyword(s):  
Ice Cover ◽  
Bed Load ◽  
Transport Capacity ◽  
Ice Jams ◽  
Frazil Ice ◽  
Ice Accumulation ◽  
River Bed ◽  
Ice Conditions ◽  
Formation And Evolution ◽  
Good Agreement

Abstract Ice jams in rivers often arise from the movement of frazil ice as cover-load under ice cover, a process which is conceptually similar to the movement of sediment as bed-load along a river bed. The formation and movement of an ice-accumulation wave is one facet of a larger class of cover-load movements. The movement of an ice-accumulation wave obviously plays a crucial role in the overall process of ice accumulation. In the present study, experiments under different flow and ice conditions help reveal the mechanics of formation and evolution of ice-accumulation waves. In particular, suitable criteria for formation of an ice-accumulation wave are investigated along with the resulting speed of wave propagation. The transport capacity of frazil ice under waved accumulation is modeled by comparing those of experiments collected in laboratories, and the resulting equation is shown to be in good agreement with measured experimental results.

scholarly journals Stratospheric Nudging And Predictable Surface Impacts (SNAPSI): A Protocol for Investigating the Role of the Stratospheric Polar Vortex in Subseasonal to Seasonal Forecasts

2022 ◽  
Author(s):  
Peter Hitchcock ◽  
Amy Butler ◽  
Andrew Charlton-Perez ◽  
Chaim Garfinkel ◽  
Tim Stockdale ◽  
...  
Keyword(s):  
Winter Season ◽  
Polar Vortex ◽  
Forecast Skill ◽  
The Arctic ◽  
Seasonal Forecasts ◽  
Stratospheric Polar Vortex ◽  
Near Surface ◽  
Forecast Models ◽  
The Impact

Abstract. Major disruptions of the winter season, high-latitude, stratospheric polar vortices can result in stratospheric anomalies that persist for months. These sudden stratospheric warming events are recognized as an important potential source of forecast skill for surface climate on subseasonal to seasonal timescales. Realizing this skill in operational subseasonal forecast models remains a challenge, as models must capture both the evolution of the stratospheric polar vortices in addition to their coupling to the troposphere. The processes involved in this coupling remain a topic of open research. We present here the Stratospheric Nudging And Predictable Surface Impacts (SNAPSI) project. SNAPSI is a new model intercomparison protocol designed to study the role of the Arctic and Antarctic stratospheric polar vortices in sub-seasonal to seasonal forecast models. Based on a set of controlled, subseasonal, ensemble forecasts of three recent events, the protocol aims to address four main scientific goals. First, to quantify the impact of improved stratospheric forecasts on near-surface forecast skill. Second, to attribute specific extreme events to stratospheric variability. Third, to assess the mechanisms by which the stratosphere influences the troposphere in the forecast models, and fourth, to investigate the wave processes that lead to the stratospheric anomalies themselves. Although not a primary focus, the experiments are furthermore expected to shed light on coupling between the tropical stratosphere and troposphere. The output requested will allow for a more detailed, process-based community analysis than has been possible with existing databases of subseasonal forecasts.

A Review of Research to Aid the Development of Commercial Arctic Marine Transportation: 1982 Trafficability Tests on the USCGC Polar Star

1985 ◽  
Vol 22 (01) ◽  
pp. 28-35
Author(s):  
Seibold Frederick
Keyword(s):  
Ice Cores ◽  
Coast Guard ◽  
The Arctic ◽  
Marine Transportation ◽  
Newport News ◽  
Research Activities ◽  
Ice Conditions ◽  
Level Ice ◽  
Ice Resistance ◽  
Resistance Tests

A multi-year "trafficability" research program was begun in 1978 to demonstrate that year-round commercial marine transportation in Arctic waters is feasible and to collect data necessary to begin developing the criteria to design and operate marine vehicles for that environment. Using U.S. Coast Guard Polar Class icebreakers, annual winter deployments had been made in 1979, 1980, and 1981 into the Bering and Chukchi Seas to collect environmental and ship performance data. Early in 1982, the fourth phase of these research activities was conducted on the USCGC Polar Star in western Alaskan waters as far north as the Arctic Circle. Participants in the research were the Maritime Administration, the U.S. Coast Guard, the State of Alaska, the Canadian Ministry of Transport, twelve participating companies of the Alaskan Oil and Gas Association, and the Newport News Shipbuilding Company. This paper reviews the results of this voyage and the data collected. The Polar Star was instrumented to continuously monitor and record propulsion and ship motion parameters and speed. Video recording equipment was used to document ice conditions. Extensive on-ice equipment was used to profile ice features and to measure other ice parameters. Numerous pressure ridges were profiled and ice cores taken to improve the understanding of Bering and Chukchi Sea winter ice conditions and ice strength. Level ice resistance tests were conducted. However, heavy level ice conditions were not encountered and it is planned to complete the level ice resistance tests in 1984. Other research tasks included an ice edge analysis, hull friction experiments, and an ice drift study.

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