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Research Papers: Offshore Technology

Numerical and Experimental Analysis of Added Resistance of Ships in Waves

[+] Author and Article Information
Ould el Moctar

Institute of Ship Technology, Ocean Engineering
and Transport Systems,
University of Duisburg-Essen,
Duisburg 47057, Germany
e-mail: ould.el-moctar@uni-due.de

Sebastian Sigmund

Institute of Ship Technology, Ocean Engineering
and Transport Systems,
University of Duisburg-Essen
Duisburg 47057, Germany
e-mail: sebastian.sigmund@uni-due.de

Jens Ley

Institute of Ship Technology, Ocean Engineering
and Transport Systems,
University of Duisburg-Essen
Duisburg 47057, Germany
e-mail: jens.ley@uni-due.de

Thomas E. Schellin

DNV GL
Hamburg 20457, Germany
e-mail: thomas.schellin@dnvgl.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 June 23, 2015; final manuscript received July 13, 2016; published online September 30, 2016. Assoc. Editor: Thomas Fu.

J. Offshore Mech. Arct. Eng 139(1), 011301 (Sep 30, 2016) (9 pages) Paper No: OMAE-15-1051; doi: 10.1115/1.4034205 History: Received June 23, 2015; Revised July 13, 2016

Two Reynolds-Averaged Navier–Stokes (RANS) based field methods numerically predicted added resistance in regular head waves for a 14,000 TEU containership and a medium size cruise ship. Long and short waves of different frequencies were considered. Added resistance was decomposed into diffraction and radiation force components, whereby diffraction forces were obtained by restraining the ship in waves and radiation forces by prescribing the motions of the ship in calm water. In short waves, the diffraction part of total resistance was dominant as almost no ship motions were induced. In long waves, the sum of diffraction and radiation forces exceeded total resistance, i.e., the interaction of these two force components, which caused the reduction of total resistance, needed to be accounted for. Predictions were compared with model test measurements. Particular emphasis was placed on the following aspects: discretization errors, frictional resistance as part of total added resistance in waves, and diffraction and radiation components of added resistance in waves. Investigations comprised two steps, namely, a preliminary simulation to determine calm water resistance and a second simulation to compute total resistance in waves, always using the same grids. Added resistance was obtained by subtracting calm water resistance from total averaged wave resistance. When frictional resistance dominated over calm water resistance, which holds for nearly all conventional ships at moderate Froude numbers, high grid densities were required in the neighborhood surrounding the hull as well as prism cells on top of the model's surface.

Copyright © 2017 by ASME
Topics: Waves , Ships , Simulation
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References

Figures

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Fig. 1

Numerical grid of a wave computation [12]

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Fig. 2

DTC global grid configuration (left) and free surface refinement and prismatic cells (right) for calm water computations

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Fig. 3

DTC calm water grid study

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Fig. 4

DTC total resistance versus model speed obtained from measurements (dashed line) and RANS computations (solid line) [12]

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Fig. 5

DTC, y+-values on hull for simulations in waves of λ/L = 1.25

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Fig. 6

DTC, wave patterns from simulations in regular head waves of λ/L = 1.25

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Fig. 7

DTC at Fn = 0.28, RAOs of added resistance in regular head waves

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Fig. 8

DTC at Fn = 0.28, RAOs of resistance in regular head waves for the fixed ship and for the ship free to heave and pitch

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Fig. 9

DTC at Fn = 0.28, time histories of resistance in regular head waves of λ/L=0.44 (top), λ/L=1 (center), and λ/L=2.5 (bottom)

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Fig. 10

Cruise ship at Fn = 0.23 on the medium grid for resistance simulations

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Fig. 11

Cruise ship at Fn = 0.23, time histories of total resistance and frictional resistance in calm water [12]

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Fig. 12

Cruise ship at Fn = 0.23, RAOs of heave (top) and pitch (bottom) in regular head waves

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Fig. 13

Cruise ship at Fn = 0.23, RAOs of added resistance in regular head waves

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Fig. 14

Cruise ship at Fn = 0.23, bow wave breaking in short regular head waves

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Fig. 15

Cruise ship at Fn = 0.23, RAOs of resistance coefficients in regular head waves

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Fig. 16

Cruise ship at Fn = 0.23, added resistance and its components from computations

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