Model Tests: LNG-Carriers in Ice

2006 ◽  
Author(s):  
Jens-Holger Hellmann ◽  
Karl-Heinz Rupp ◽  
Walter L. Kuehnlein
Keyword(s):  
Natural Gas ◽  
Model Tests ◽  
Ice Thickness ◽  
New Developments ◽  
Ship Building ◽  
Future Performance ◽  
Level Ice ◽  
Ice Navigation ◽  
Parental Level ◽  
Ice Model

Approximately on third of the world’s known and not yet exploited reserves of natural gas are in Russia. The overwhelming majority of these reserves are in Artic and Subarctic areas. But not only in Russia, also in other areas like Canada and USA, natural gas reserves are found in harsh and ice covered environments. As a consequence, the LNG ship technology is going towards Arctic LNG-Carriers. New developments in ice navigation, winterization and ship sizes are generating a new exiting challenge for shipping and ship building industries all over the world. Existing ice class regulations should be only considered as a first guide for designing ice-going vessels. Because the future performance in ice covered waters of new developed LNG-Carriers needs to be investigated in much more detail, therefore ice model tests are imperative. It is common practice guiding ships in ice-covered waters by using one or two icebreakers for wider LNG-Carriers. The LNG-Carrier is following in the broken channel of about 1.25 to 2 times the widths of its beam. For the model tests a parental level ice sheet of target ice thickness will be prepared according to HSVA’s standard model ice preparation procedure. In order to obtain a defined friction coefficient between the ice and the model hull, HSVA applies a special paint composition to the models of ice-going vessels. The channel will be broken with the help of two stock icebreakers towed through the level ice generating the most realistic wide ice channel. The prime objectives of such ice model tests are: • Evaluation of the icebreaking performance in a wide ice channel, • Propeller-ice-interactions and • how the ice is transferred aside and below the vessel.

Model Tests in Brash Ice Channels

2005 ◽  
Author(s):  
Jens-Holger Hellmann ◽  
Karl-Heinz Rupp ◽  
Walter L. Kuehnlein
Keyword(s):  
Perforated Plate ◽  
Ice Sheet ◽  
Open Water ◽  
Model Tests ◽  
Ice Thickness ◽  
Special Device ◽  
Level Ice ◽  
Set Up ◽  
Parental Level ◽  
Oil Tankers

According to the present Finnish-Swedish Ice Class Rules (FSICR) the formulas for the required main engine power for tankers led to much bigger main engines than it is needed for the demanded open water speed. Therefore model tests may be performed in order to verify the vessel’s capability to sail with less required power in brash ice channels compared to the calculations. Several model test runs have been performed in order to study the performance of crude oil tankers sailing in brash ice. The tests were performed as towed propulsion tests and the brash ice channel was prepared according to the guidelines set up by the Finnish Maritime Administration (FMA). The channel width was 2 times the beam of the tanker. The model tests were carried out at a speed of 5 knots. For the tests a parental level ice sheet of adequate thickness is prepared according to HSVA’s standard model ice preparation procedure. After a predefined level ice thickness has been reached, the air temperature in the ice tank will be raised. An ice channel with straight edges will be cut into the ice sheet by means of two ice knives. The ice stripe between the two cuts will be manually broken up into relatively small ice pieces using a special ice chisel and if required the brash ice material will be compacted. Typically the brash ice thickness will be measured prior the tests at 9 positions across the channel and every two meter over the entire length of the brash ice channel with a special device, which consists of a measuring rule with a perforated plate mounted under a right angle at the lower end of the rule. As a result of the tests it could be demonstrated that tankers with a capacity of more than 50 000 tons require 50% and even less power compared to calculations using the present FSICR formulas.

The Resistance of Ice Breaking Ships Based on Model Tests

2015 ◽  
Author(s):  
Seong-Rak Cho ◽  
Kuk-Jin Kang ◽  
Sungsu Lee
Keyword(s):  
Model Tests ◽  
Design Stage ◽  
Preliminary Design ◽  
Factors Associated ◽  
Preliminary Design Stage ◽  
Level Ice ◽  
Resistance Prediction ◽  
Ice Resistance ◽  
Priority Factor ◽  
Ice Model

The two most important tasks of ice breaking ships are first to secure a sailing route by breaking the thick sea ice and second to sail efficiently herself for purposes of exploration and transportation in the polar seas. The resistance of ice breaking ships is a priority factor at the preliminary design stage; not only must their sailing efficiency be satisfied, but the design of the propulsion system will be directly affected. Therefore, the performance of ice-breaking ships must be accurately calculated and evaluated through the use of model tests in an ice model basin before construction starts. In this paper, a new procedure is developed, based on model tests, to estimate a ship’s ice resistance during continuous icebreaking in level ice. Some of the factors associated with crushing failures are systematically considered in order to correctly estimate her ice-breaking resistance, while the effects of the hull geometry, as reflected in the length, breadth, and draft of ships, are considered in calculating buoyancy and clearing resistance. Multiple regression analysis is calculated with each ice resistance component. This study is intended to contribute to the improvement of the techniques for ice resistance prediction with ice breaking ships.

Methodology to Investigate the Icebreaking Process of Ships With Non-Typical Icebreaking Bow Shapes

2020 ◽  
Author(s):  
Quentin Hisette ◽  
Daniela Myland
Keyword(s):  
Ice Sheets ◽  
Relevant Information ◽  
Model Tests ◽  
Interaction Process ◽  
Analysis Procedure ◽  
Load Cells ◽  
Level Ice ◽  
Ice Resistance ◽  
Different Thickness ◽  
Ice Model

Abstract For non-typical icebreaking ships the hull-ice interaction process in level ice comprises a combination of many different phenomena which is difficult to be described by existing straightforward approaches. In order to gain knowledge about the level ice resistance of such non-typical hull shapes for operation in ice, a methodology is developed and presented to identify and evaluate the level ice resistance as well as its distribution along the hull of ships with non-typical icebreaking bow shapes with high stem and/or small waterline angles. For this purpose, one ship model has been manufactured and instrumented with several multi-component load cells in the bow region of the waterline as well as with one large six-component load scale between the bow and the stern. Performing resistance model tests at several loading conditions, in model ice sheets of different thickness and at multiple speed values allows obtaining relevant information to meet the goals of the study. The paper focuses on the methodology used for the ice model tests and its analysis. Instrumentation of the model is fully described, together with an overview of the testing matrix and model test observations. Analysis procedure is described in details and applied on a representative test run of the campaign.

Model Tests With a Compliant Cylindrical Structure to Investigate Ice-Induced Vibrations

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Gesa Ziemer ◽  
Karl-Ulrich Evers
Keyword(s):  
Natural Frequency ◽  
Structural Response ◽  
Model Tests ◽  
Ice Thickness ◽  
Cylindrical Structure ◽  
Ice Drift ◽  
Wide Range ◽  
Dynamic Forces ◽  
Dynamic Amplification ◽  
Ice Model

A compliant cylindrical structure has been built and tested in a series of model tests in ice in the Large Ice Model Basin at HSVA. The structure's stiffness in ice plane is higher in ice drift direction than crosswise, enabling the model to vibrate in different geometrical oscillation patterns. In total, four ice sheets have been used to perform tests in different ice thickness, covering a wide range of ice drift velocities between 0.005 and 0.15 m/s in model scale. Several events of ice-induced vibrations were observed throughout the test campaign. Oscillations are found to reach different types of beginning steady states, depending on ice drift velocity and ice thickness. Dynamic amplification of structural response in ice plane as well as ratio of static and dynamic forces is highly dependent on the type of vibration. While the dynamic amplification is highest when the ice load's frequency equals the first natural frequency of the structure, the highest dynamic forces occur when the crushing frequency is an integer fraction of the natural frequency. The paper describes the design of the test setup, instrumentation and calibration, performance and analysis of conducted tests, and general findings.

Ice Model Tests With a Compliant Cylindrical Structure to Investigate Ice-Induced Vibrations

2014 ◽  
Author(s):  
Gesa Ziemer ◽  
Karl-Ulrich Evers
Keyword(s):  
Natural Frequency ◽  
Structural Response ◽  
Model Tests ◽  
Ice Thickness ◽  
Cylindrical Structure ◽  
Ice Drift ◽  
Wide Range ◽  
Dynamic Forces ◽  
Dynamic Amplification ◽  
Ice Model

A compliant cylindrical structure has been built and tested in a series of model tests in ice in the Large Ice Model Basin at HSVA. The structure’s stiffness in ice plane is higher in ice-drift direction than crosswise, enabling the model to vibrate in different oscillation patterns. In total, 4 ice sheets have been used to perform tests in different ice thickness, covering a wide range of ice drift velocities between 0.005 and 0.15 m/s in model scale. Several events of ice-induced vibrations were observed throughout the test campaign. Oscillations are found to reach different types of beginning steady-state, mainly depending on ice drift velocity and ice thickness. Dynamic amplification of structural response in ice plane as well as ratio of static and dynamic forces is highly dependent on the type of vibration. While the dynamic amplification is highest when the ice load’s frequency equals the first natural frequency of the structure, the highest dynamic forces occur when the crushing frequency is an integer fraction of the natural frequency. The paper describes the design of the test set-up, instrumentation and calibration, performance and analysis of conducted tests, and general findings.

scholarly journals Formulation of Ice Resistance in Level Ice Using Double-Plates Superposition

2020 ◽  
Vol 8 (11) ◽  
pp. 870
Author(s):  
Liang Li ◽  
Qingfei Gao ◽  
Alexander Bekker ◽  
Hongzhe Dai
Keyword(s):  
Elastic Plate ◽  
Approximate Model ◽  
Ice Thickness ◽  
Full Scale Test ◽  
Ship Resistance ◽  
Bending Resistance ◽  
Level Ice ◽  
Scale Test ◽  
Coulomb Criterion ◽  
Ice Resistance

The estimation of ship resistance in ice is a fundamental area of research and poses a substantial challenge for the design and safe use of ships in ice-covered waters. In order to estimate the ice resistance with greater reliability, we develop in this paper an improved Lindqvist formulation for the estimation of bending resistance in level ice based on the superposition of double-plates. In the developed method, an approximate model of an ice sheet is firstly presented by idealizing ice sheeta as the combination of a semi-infinite elastic plate and an infinite one resting on an elastic foundation. The Mohr–Coulomb criterion is then introduced to determine the ice sheet’s failure. Finally, an improved Lindqvist formulation for estimation of ice resistance is proposed. The accuracy of the developed formulation is validated using full-scale test data of the ship KV Svalbard in Norway, testing the model as well as the numerical method. The effect of ice thickness, stem angle and breadth of bow on ship resistance is further investigated by means of the developed formulation.

Advanced Weathervaning in Ice

2011 ◽  
Author(s):  
William Hidding ◽  
Guillaume Bonnaffoux ◽  
Mamoun Naciri
Keyword(s):  
Rapid Change ◽  
Ice Sheet ◽  
Model Tests ◽  
The Arctic ◽  
Mooring System ◽  
Sudden Increase ◽  
Time Step ◽  
Ice Loads ◽  
Level Ice ◽  
Drift Direction

The reported presence of one third of remaining fossil reserves in the Arctic has sparked a lot of interest from energy companies. This has raised the necessity of developing specific engineering tools to design safely and accurately arctic-compliant offshore structures. The mooring system design of a turret-moored vessel in ice-infested waters is a clear example of such a key engineering tool. In the arctic region, a turret-moored vessel shall be designed to face many ice features: level ice, ice ridges or even icebergs. Regarding specifically level ice, a turret-moored vessel will tend to align her heading (to weather vane) with the ice sheet drift direction in order to decrease the mooring loads applied by this ice sheet. For a vessel already embedded in an ice sheet, a rapid change in the ice drift direction will suddenly increase the ice loads before the weathervaning occurs. This sudden increase in mooring loads may be a governing event for the turret-mooring system and should therefore be understood and simulated properly to ensure a safe design. The paper presents ADWICE (Advanced Weathervaning in ICE), an engineering tool dedicated to the calculation of the weathervaning of ship-shaped vessels in level ice. In ADWICE, the ice load formulation relies on the Croasdale model. Ice loads are calculated and applied to the vessel quasi-statically at each time step. The software also updates the hull waterline contour at each time step in order to calculate precisely the locations of contact between the hull and the ice sheet. Model tests of a turret-moored vessel have been performed in an ice basin. Validation of the simulated response is performed by comparison with model tests results in terms of weathervaning time, maximum mooring loads, and vessel motions.

scholarly journals Simulation of Snow on Arctic Sea Ice Using a Coupled Snow–Ice Model

2010 ◽  
Vol 11 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Yi-Ching Chung ◽  
Stéphane Bélair ◽  
Jocelyn Mailhot
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Snow Depth ◽  
Single Layer ◽  
Coupled System ◽  
The Arctic ◽  
Ice Thickness ◽  
The Arctic Ocean ◽  
Snow Model ◽  
Ice Model

Abstract The new Recherche Prévision Numérique (NEW-RPN) model, a coupled system including a multilayer snow thermal model (SNTHERM) and the sea ice model currently used in the Meteorological Service of Canada (MSC) operational forecasting system, was evaluated in a one-dimensional mode using meteorological observations from the Surface Heat Budget of the Arctic Ocean (SHEBA)’s Pittsburgh site in the Arctic Ocean collected during 1997/98. Two parameters simulated by NEW-RPN (i.e., snow depth and ice thickness) are compared with SHEBA’s observations and with simulations from RPN, MSC’s current coupled system (the same sea ice model and a single-layer snow model). Results show that NEW-RPN exhibits better agreement for the timing of snow depletion and for ice thickness. The profiles of snow thermal conductivity in NEW-RPN show considerable variability across the snow layers, but the mean value (0.39 W m−1 K−1) is within the range of reported observations for SHEBA. This value is larger than 0.31 W m−1 K−1, which is commonly used in single-layer snow models. Of particular interest in NEW-RPN’s simulation is the strong temperature stratification of the snowpack, which indicates that a multilayer snow model is needed in the SHEBA scenario. A sensitivity analysis indicates that snow compaction is also a crucial process for a realistic representation of the snowpack within the snow/sea ice system. NEW-RPN’s overestimation of snow depth may be related to other processes not included in the study, such as small-scale horizontal variability of snow depth and blowing snow processes.

The Mooring Bay Concept for LNG Loading in Harsh and Ice Conditions

2012 ◽  
Author(s):  
Sven Hoog ◽  
Joachim Berger ◽  
Johannes Myland ◽  
Günther F. Clauss ◽  
Daniel Testa ◽  
...  
Keyword(s):  
Natural Gas ◽  
Model Tests ◽  
The Arctic ◽  
Transfer System ◽  
Research Project ◽  
Joint Research ◽  
Gas Treatment ◽  
Ice Coverage ◽  
Joint Research Project ◽  
Flexible Transfer Lines

The demand for natural gas from offshore fields is continuously increasing. Especially future production from Arctic waters comes into focus in context with global warming effects leading to the development of a dedicated technology. Relevant approaches work with floating turret moored production terminals (FLNG) receiving gas via flexible risers from subsea or onshore fields. These terminals provide on-board gas treatment and liquefaction facilities as well as huge storage capabilities for LNG (Liquefied Natural Gas), LPG (Liquefied Petrol Gases) and condensate. Products are transferred to periodically operating shuttle tankers for onshore supply reducing the need for local onshore processing plants providing increased production flexibility (future movability or adaptation of capacity). Nevertheless, in case of harsh environmental conditions or ice coverage the offshore transfer of cryogenic liquids between the terminal and the tankers becomes a major challenge. In the framework of the joint research project MPLS20 ([1]), an innovative offshore mooring and cargo transfer system has been developed and analyzed. MPLS20 is developed by the project partners Nexans ([2]) and Brugg ([3]), leading manufacturers of vacuum insulated, flexible cryogenic transfer pipes, IMPaC ([4]), an innovative engineering company that has been involved in many projects for the international oil and gas industry for more than 25 years and the Technical University (TU) Berlin, Department of Land- and Sea Transportation Systems (NAOE, [5]), with great expertise in numerical analyses and model tests. The overall system is based on IMPaC’s patented and certified offshore ‘Mooring Bay’ concept allowing mooring of the vessels in tandem configuration and simultaneous handling and operation of up to six flexible transfer pipes in full aerial mode. The concept is outlined to operate with flexible transfer lines with 16-inch inner diameter like the newly designed and certified corrugated pipes from Nexans and Brugg. The mooring concept and its major subsystems have proven their operability by means of extensive numerical analysis, model tests and a professional ship handling simulator resulting in an overall transfer solution suitable to be used especially under Arctic conditions like addressed by the EU joint research project ACCESS (http://access-eu.org/). The paper introduces the new offshore LNG transfer system and focuses especially on its safe and reliable operability in the Arctic — with ice coverage as well as in open water conditions.

scholarly journals On the discretization of the ice thickness distribution in the NEMO3.6-LIM3 global ocean–sea ice model

2019 ◽  
Vol 12 (8) ◽  
pp. 3745-3758 ◽  
Author(s):  
François Massonnet ◽  
Antoine Barthélemy ◽  
Koffi Worou ◽  
Thierry Fichefet ◽  
Martin Vancoppenolle ◽  
...  
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Large Scale ◽  
Thickness Distribution ◽  
Circulation Model ◽  
Grid Cell ◽  
The Arctic ◽  
Global Ocean ◽  
Ice Thickness ◽  
Ice Model

Abstract. The ice thickness distribution (ITD) is one of the core constituents of modern sea ice models. The ITD accounts for the unresolved spatial variability of sea ice thickness within each model grid cell. While there is a general consensus on the added physical realism brought by the ITD, how to discretize it remains an open question. Here, we use the ocean–sea ice general circulation model, Nucleus for European Modelling of the Ocean (NEMO) version 3.6 and Louvain-la-Neuve sea Ice Model (LIM) version 3 (NEMO3.6-LIM3), forced by atmospheric reanalyses to test how the ITD discretization (number of ice thickness categories, positions of the category boundaries) impacts the simulated mean Arctic and Antarctic sea ice states. We find that winter ice volumes in both hemispheres increase with the number of categories and attribute that increase to a net enhancement of basal ice growth rates. The range of simulated mean winter volumes in the various experiments amounts to ∼30 % and ∼10 % of the reference values (run with five categories) in the Arctic and Antarctic, respectively. This suggests that the way the ITD is discretized has a significant influence on the model mean state, all other things being equal. We also find that the existence of a thick category with lower bounds at ∼4 and ∼2 m for the Arctic and Antarctic, respectively, is a prerequisite for allowing the storage of deformed ice and therefore for fostering thermodynamic growth in thinner categories. Our analysis finally suggests that increasing the resolution of the ITD without changing the lower limit of the upper category results in small but not negligible variations of ice volume and extent. Our study proposes for the first time a bi-polar process-based explanation of the origin of mean sea ice state changes when the ITD discretization is modified. The sensitivity experiments conducted in this study, based on one model, emphasize that the choice of category positions, especially of thickest categories, has a primary influence on the simulated mean sea ice states while the number of categories and resolution have only a secondary influence. It is also found that the current default discretization of the NEMO3.6-LIM3 model is sufficient for large-scale present-day climate applications. In all cases, the role of the ITD discretization on the simulated mean sea ice state has to be appreciated relative to other influences (parameter uncertainty, forcing uncertainty, internal climate variability).

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