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Research Papers: Ocean Engineering

A Computationally Efficient Implementation of Nonzero-Speed Transient Green Functions for Zero-Speed Nonlinear Seakeeping Problems

[+] Author and Article Information
G. D. Gkikas

MARIN,
Haagsteeg 2,
Wageningen 6708 PM, The Netherlands
e-mails: georgios.gkikas@sbmoffshore.com;
geogikas@gmail.com

F. van Walree

MARIN,
Haagsteeg 2,
Wageningen 6708 PM,
The Netherlands
e-mail: F.v.Walree@marin.nl

1Corresponding author.

2Present address: SBM Offshore, Karel Doormanweg 66, 3115 JD Schiedam, Postbus 11, Schiedam 3100 AA, The Netherlands.

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 25, 2015; final manuscript received September 3, 2016; published online October 18, 2016. Assoc. Editor: Robert Seah.

J. Offshore Mech. Arct. Eng 139(1), 011102 (Oct 18, 2016) (10 pages) Paper No: OMAE-15-1016; doi: 10.1115/1.4034694 History: Received February 25, 2015; Revised September 03, 2016

The proposed methodology is a time-domain panel method where the transient Green functions (GFs) used for the estimation and implementation of the free-surface effects on the vessel's motions are estimated assuming constant low lateral speed, instead of the common practice zero-speed influence functions. The main difference between the proposed method and standard practice lies in the use of the proposed scheme on a typical zero-speed problem, as the solution scheme is conditioned to the mean drift velocity instead of zero-speed. Furthermore, in this way, a significant improvement in accuracy accompanied by a large reduction in computational times is also achieved. The low lateral-speed GFs are computed for a speed similar to the one that the vessel is expected to drift. Estimation of this speed can be initially based on model tests or by means of an iterative process where we start the computations with the zero-speed GFs and adjust the latter's input speed according to the calculated drift speed until convergence is obtained. As a representative case study, we apply this method for the simulation of seakeeping behavior of a cruise ship in extreme dead ship conditions. For the validation of the proposed methodology, the first- and second-order motions, i.e., heave, roll, and the drift velocity, respectively, as well as lateral accelerations of the vessel were investigated for two cases of severe beam seas further combined with a constant strong wind load. The results were compared against experimental model tests.

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References

Figures

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Fig. 1

Schematic representation of the vessel with respect to space and ship coordinate systems

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Fig. 2

Numerical and experimental wave spectrums corresponding to case I, i.e., HS = 9.0 m and TP = 16.9 s

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Fig. 3

Numerical and experimental wave spectrums corresponding to case II, i.e., HS = 11.65 m and TP = 19.0 s

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Fig. 4

Comparison of experimental and simulated results for the mean and the standard deviation of the heave response for the beam seas case I. The integers at the x-axis correspond to the configurations presented in Table 4.

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Fig. 5

Same as in Fig. 4, but for the roll response

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Fig. 6

Same as in Fig. 4, but for the drift velocity

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Fig. 7

Comparison of experimental and simulated mean heave response for the beam seas case II. The integers in the x-axis correspond to the configurations presented in Table 5.

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Fig. 8

Same as in Fig. 7, but for the roll response

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Fig. 9

Same as in Fig. 7, but for the drift velocity

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Fig. 10

Comparison of experimental and simulated lateral accelerations for the beam seas case I

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Fig. 11

Same as in Fig. 10, but for the beam seas case II

Tables

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