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Research Papers: Polar and Arctic Engineering

Experimental and Numerical Investigation of Dynamic Positioning in Level Ice

[+] Author and Article Information
Ivan Metrikin

Department of Civil and Transport Engineering,
Norwegian University of Science and Technology,
Trondheim 7491, Norway;
Arctic Design and Operations,
Statoil ASA,
Trondheim 7053, Norway
e-mail: ivan.metrikin@ntnu.no

Sofien Kerkeni

D-ICE Engineering,
Nantes 44000, France;
DCNS Research/Sirehna,
Nantes 44300, France

Peter Jochmann

Ice and Offshore Department,
Hamburg Ship Model Basin,
Hamburg 22305, Germany

Sveinung Løset

Department of Civil and Transport Engineering,
Norwegian University of Science and Technology,
Trondheim 7491, Norway

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received September 6, 2013; final manuscript received March 8, 2015; published online April 8, 2015. Assoc. Editor: Søren Ehlers.

J. Offshore Mech. Arct. Eng 137(3), 031501 (Jun 01, 2015) (10 pages) Paper No: OMAE-13-1085; doi: 10.1115/1.4030042 History: Received September 06, 2013; Revised March 08, 2015; Online April 08, 2015

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.

Copyright © 2015 by ASME
Topics: Ice , Vessels , Simulation
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References

Figures

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Fig. 1

Sketch of the large ice model basin of HSVA

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Fig. 2

Body plan of the DP vessel: Left: bow view and right: stern view

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Fig. 3

Model of the DP vessel: Left: bow view and right: stern view. White marks indicate the waterline.

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Fig. 4

Propellers of the DP vessel: Left: bow propellers (all three are the same), middle: stern starboard (same as stern port), and right: stern center

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Fig. 5

Thrust–RPS relationship for the propellers of the DP vessel

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Fig. 6

Experimental setup for DP in level ice

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Fig. 7

Trace of the DP vessel in ice basin trials

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Fig. 8

Heading offset of the DP vessel in ice basin trials

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Fig. 9

Ice loads on the DP vessel in ice basin trials

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Fig. 10

Trajectories of the ice motion around the vessel seen from underwater cameras: Left: port side and right: starboard side

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Fig. 11

Cusps and wedges of broken ice in the channel behind the DP vessel

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Fig. 12

Drillship on DP at 15 deg oblique angle in level ice

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Fig. 13

Trace of the DP vessel at 0 deg ice drift angle

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Fig. 14

Ice loads estimated by the DP system at 0 deg ice drift angle

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Fig. 15

Surface mesh of the DP vessel used in numerical simulations

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Fig. 16

Screenshots from a numerical simulation of DP in level ice

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Fig. 17

Simulated trace of the DP vessel at 0 deg ice drift angle

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Fig. 18

Ice loads estimated by the DP system at 0 deg ice drift angle in simulation

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Fig. 19

Estimated ice loads on the DP vessel in simulations at high ice drift angles

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Fig. 20

Trace of the DP vessel in simulations at high ice drift angles

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Fig. 21

Comparison between experiments and simulation at 30 deg ice drift angle

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