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Ocean Engineering

Hydroelastic Behaviors of VLFS Supported by Many Aircushions With the Three-Dimensional Linear Theory

[+] Author and Article Information
Tomoki Ikoma

Department of Oceanic Architecture and Engineering, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501, Japanikoma.tomoki@nihon-u.ac.jp

Koichi Masuda

Department of Oceanic Architecture and Engineering, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501, Japanmasuda.koiichi@nihon-u.ac.jp

Chang-Kyu Rheem

Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japanrheem@iis.u-tokyo.ac.jp

Hisaaki Maeda

Department of Oceanic Architecture and Engineering, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501, Japanmaedah@iis.u-tokyo.ac.jp

J. Offshore Mech. Arct. Eng 134(1), 011104 (Oct 17, 2011) (8 pages) doi:10.1115/1.4003697 History: Received May 24, 2010; Revised November 29, 2010; Published October 17, 2011; Online October 17, 2011

This paper describes hydroelastic motion and effect of motion reduction of large floating structures in head sea conditions, supported by aircushion. Motion reduction effects, appearing due to the presence of aircushions, have been confirmed through theoretical calculations with the zero-draft assumption. Three-dimensional prediction method has been developed for evaluating draft influence of division walls of aircushions. Using three-dimensional theoretical calculations, authors have investigated whether hydroelastic motion reduction is possible or not. Next, aircushion type bodies were supported by multiple aircushions, which are smaller in size than the wavelengths. Green’s function method within the linear potential theory was applied for prediction of hydrodynamic forces and wave excitations, in which the effect of free water surface between aircushions was considered. Hydroelastic responses were estimated not only in terms of elastic motion, but also in terms of vertical bending moment. The results confirmed the existence of response reduction, especially noticeable for the vertical bending moment in a wide wavelength range and in the whole structure area.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Coordinate system

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Figure 2

Basic horizontal plane for all pontoon types and all aircushion types

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Figure 5

Aircushion arrangement of aircushion Type C

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Figure 6

Section of aircushion types and definition of skirt draft

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Figure 7

Comparison of vertical displacement of models with D=1.52×1011 N m, L/λ=4.45, on y=0

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Figure 8

Comparison of vertical displacement of models with D=1.52×1011 N m, L/λ=6.67, on y=0

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Figure 9

Comparison of vertical displacement of models with D=1.52×1011 N m, L/λ=7.91, on y=0

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Figure 13

Comparison of vertical displacement of models with D=1.52×1010 N m, L/λ=6.67, on y=0

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Figure 14

Comparison of vertical displacement of models with D=1.52×1010 N m, L/λ=7.91, on y=0

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Figure 15

Comparison of vertical displacement of models with D=1.52×1010 N m, L/λ=9.0, on y=0

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Figure 17

Comparison of vertical bending moment of models with D=1.52×1011 N m, L/λ=4.45, on y=0

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Figure 18

Comparison of vertical bending moment of models with D=1.52×1011 N m, L/λ=6.67, on y=0

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Figure 19

Comparison of vertical bending moment of models with D=1.52×1011 N m, L/λ=7.91, on y=0

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Figure 20

Comparison of vertical bending moment of models with D=1.52×1011 N m, L/λ=9.0, on y=0

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Figure 21

Comparison of vertical bending moment of models with D=1.52×1011 N m, L/λ=10.0, on y=0

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Figure 22

Comparison of vertical bending moment of models with D=1.52×1010 N m, L/λ=4.45, on y=0

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Figure 23

Comparison of vertical bending moment of models with D=1.52×1010 N m, L/λ=6.67, on y=0

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Figure 24

Comparison of vertical bending moment of models with D=1.52×1010 N m, L/λ=7.91, on y=0

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Figure 25

Comparison of vertical bending moment of models with D=1.52×1010 N m, L/λ=9.0, on y=0

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Figure 26

Comparison of vertical bending moment of models with D=1.52×1010 N m, L/λ=10.0, on y=0

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Figure 27

Singular integral regions of circle and others planes

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Figure 28

Variation of radius rn to apply asymptotic function of K0

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Figure 29

Difference of minute circle area and analytical singular integral area

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Figure 30

Numerical integration of side panels

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Figure 31

Variation of radius rn to apply asymptotic function of K0

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Figure 16

Comparison of vertical displacement of models with D=1.52×1010 N m, L/λ=10.0, on y=0

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Figure 10

Comparison of vertical displacement of models with D=1.52×1011 N m, L/λ=9.0, on y=0

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Figure 4

Aircushion arrangement of aircushion Type B

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Figure 12

Comparison of vertical displacement of models with D=1.52×1010 N m, L/λ=4.45, on y=0

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Figure 11

Comparison of vertical displacement of models with D=1.52×1011 N m, L/λ=10.0, on y=0

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Figure 3

Aircushion arrangement of aircushion Type A

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