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Research Papers: Ocean Engineering

A Novel Restraining System for a Powerless Advancing Ship: A Combined Theoretical and Experimental Investigation

[+] Author and Article Information
Xu-jun Chen

College of Field Engineering,
PLA University of Science and Technology,
Nanjing 210007, China;
China Ship Scientific Research Center,
Wuxi 214082, China
e-mail: chenxujun213@sina.com

Jun-yi Liu

College of Field Engineering,
PLA University of Science and Technology,
Nanjing 210007, China;
Fluid Structure Interactions Research Group,
University of Southampton,
Southampton SO16 7QF, UK
e-mail: liujunyi_1988@outlook.com

Grant E. Hearn

Fluid Structure Interactions Research Group,
University of Southampton,
Southampton SO16 7QF, UK
e-mail: g.e.hearn@soton.ac.uk

Ye-ping Xiong

Fluid Structure Interactions Research Group,
University of Southampton,
Southampton SO16 7QF, UK
e-mail: Y.Xiong@soton.ac.uk

Guang-huai Wu

College of Field Engineering,
PLA University of Science and Technology,
Nanjing 210007, China
e-mail: gh-wu@sohu.com

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received February 5, 2016; final manuscript received August 21, 2016; published online November 29, 2016. Assoc. Editor: Ron Riggs.

J. Offshore Mech. Arct. Eng 139(1), 011103 (Nov 29, 2016) (14 pages) Paper No: OMAE-16-1017; doi: 10.1115/1.4034821 History: Received February 05, 2016; Revised August 21, 2016

A novel flexible restraining system is proposed to protect a waterway crossing road, a railway, or a combined bridge when a powerless advancing ship approaches such a structure. Direct collision with principal bridge supports is not addressed under the assumption that the restraining system is located some distance upstream of the non-navigational bridge, assuming the ship cannot engage propulsive system in reverse to reduce the speed of ship advance. Ship-independent seabed-located gravity anchors are to be ultimately dragged to dissipate ship kinetic energy. A mathematical model of the proposed method of restraint is developed and the resulting movements of ship and anchors are predicted for two distinct ship forms. These ships' responses are investigated for initial ship velocity, angle of approach, and point of contact with restraining cable of different investigated spans in the presence and absence of a current. The theoretical simulations agree reasonably well with the related model measurements given the existence of ship sway and yaw motions are not addressed. The results are sufficient to demonstrate the applicability of the proposed system. Predictions and observations suggest that the smaller the restraining cable span and the closer the ship is located to the anchors (initially vertically below the ends of the restraining cable), the more effective is the retraining process.

Copyright © 2017 by ASME
Topics: Ships , Cables
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References

Figures

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Fig. 1

Front elevation and plan of a single unit of overhead retardation system

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Fig. 2

Force and velocity components used in theoretical analysis

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Fig. 3

Geometric relationships related to ship and anchor movements: (a) principal parameters illustrated and (b) plan view of ship and restraining system

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Fig. 4

Calculation flowchart for velocity reduction and energy dissipation approaches

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Fig. 5

Realistic anchor arrangement and schematic anchor with pertinent forces indicated: (a) anchor on seabed and (b) anchor on the tank bottom

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Fig. 6

Sketches illustrating different aspects of restraining system: (a) different configurations of the restraining system and (b) sketch of restraining cable support and designed weak point

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Fig. 8

Anchor movements in still water for cable span of 8 m: (a) collision point at xc=4.0m, (b) collision point at xc=5.6m, and (c) collision point at xc=7.2m

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Fig. 9

Anchor movements in a steady current for cable span of 8 m: (a) collision point at xc=4.0m, (b) collision point at xc=5.6m, and (c) collision point at xc=7.2m

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Fig. 10

Collision in current for cable span of 4.8 m at xc=2.4m: (a) 76 kg ship model and (b) 200 kg ship model

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Fig. 11

Collision in current for cable span of 4.8 m at xc=4.0m: (a) 76 kg ship model and (b) 200 kg ship model

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Fig. 12

A 76 kg ship model collides at xc=1.2m for span of 2.4 m with current: (a) Impact angle is 30 deg, (b) impact angle is 60 deg (c) impact angle is 90 deg, and (d) impact angle is 120 deg

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Fig. 13

A 200 kg ship model collides at xc=1.2m for span of 2.4 m with current: (a) Impact angle is 30 deg, (b) impact angle is 60 deg, (c) impact angle is 90 deg, and (d) impact angle is 120 deg

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Fig. 14

A 76 kg ship model collides at xc=1.8m for span of 2.4 m with current: (a) Impact angle is 60 deg, (b) impact angle is 90 deg, and (c) impact angle is 120 deg

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Fig. 15

A 200 kg ship model collides at xc=1.8m for span of 2.4 m with current: (a) Impact angle is 60 deg, (b) impact angle is 90 deg, and (c) impact angle is 120 deg

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Fig. 16

Percentage relative errors in anchor movement for different initial ship speeds: (a) relative error range characteristics and (b) frequency of relative errors between ±20%

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Fig. 17

Ship movements in a current for a ship of mass 9500t approaching head-on a restraining system of differing span

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Fig. 18

Ship movements in a current for a ship of mass 9500t approaching head-on a 400 m restraining system at different locations

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Fig. 19

Ship movements in otherwise still water for a ship of mass 9500t approaching head-on a 400 m restraining system at different locations

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Fig. 20

Ship movements in a current for a ship of mass 9500t approaching a 120 m restraining system at different angles at the location xc=90m

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Fig. 21

Ship movements in a current for a ship of mass 25,000t approaching a 120 m restraining system at different angles at the location xc=90m

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