A Research on Characteristics of Responses of a Floating Structure in Tsunami

2004 ◽  
Author(s):  
Koichi Masuda ◽  
Tomoki Ikoma ◽  
Maki Uchida ◽  
Akira Takeda
Keyword(s):  
Wave Theory ◽  
Floating Body ◽  
Present System ◽  
Convolution Integral ◽  
Floating Bodies ◽  
Floating Structure ◽  
Exciting Forces ◽  
Mooring Forces ◽  
Analysis System ◽  
Present Simulation

The objective of present paper are to establish the practical numerical analysis system for responses of motions and mooring forces on a floating structure induced by Tsunami and to clarify the characteristics of responses on floating bodies in tsunami. In the present analysis system, the initial tsunami profile is evaluated by Mansinha-Smylie’s Method and propagating tsunami profiles are calculated by linear long wave theory and also the tsunami exciting forces on floating body are computed by the numerical wave tank based on VOF method [5] and then the motions and mooring tether forces due to Tsunami on floating body are predicted by the convolution integral method. The usefulness of present system is confirmed by comparing with the experimental results on Tsunami exciting forces on floating bodies. The responses of floating body due to tsunami using fault models of Tokai and Tonankai earthquakes are computed by using the present simulation system so that the characteristics of responses on floating bodies are examined and are clarified.

Comparisons of Simulation Methods for Motions of a Moored Body in Waves

1985 ◽  
Vol 107 (1) ◽  
pp. 34-41
Author(s):  
M. Takagi ◽  
K. Saito ◽  
S. Nakamura
Keyword(s):  
Wave Theory ◽  
Simulation Methods ◽  
Convolution Integral ◽  
Linear Water Wave Theory ◽  
Initial Stage ◽  
Constant Coefficients ◽  
Exciting Forces ◽  
Linear Differential ◽  
Experimental Values ◽  
The Time Domain

Based on the linear water wave theory, numerical simulations are carried out for motions in waves of a body moored by a nonlinear-type mooring system. Numerical results obtained by using the equation of motion described in the time domain with a convolution integral (C.I. method) are compared with those of the second-order linear differential equation with constant coefficients (C. C. method). These results are also compared with experimental values measured from the initial stage when the action of exciting forces starts and the validity of C.I. method is discussed.

Behavior of the Pontoon Supported by Mooring Dolphin in Tsunami

2011 ◽  
Author(s):  
Mitsuhiro Masuda ◽  
Koichi Masuda ◽  
Tomoki Ikoma ◽  
Kuniaki Shouji
Keyword(s):  
Solitary Wave ◽  
Simulation System ◽  
Container Terminals ◽  
Floating Body ◽  
Mooring System ◽  
Disaster Prevention ◽  
Floating Structure ◽  
Marine Disaster ◽  
Floating Type ◽  
Present Simulation

In recent years, the floating facilities for the ocean space utilization such as the marine disaster prevention base, the floating restaurant, floating type container terminals are planned and some of those facilities are actually built. Most of these facilities are the pontoon type floating structure, and the mooring system is a mooring dolphin. In the design of such facilities, it is important that the prediction of the behavior of the pontoon type floating body supported by mooring dolphin in tsunami the objective of present research is to develop the simulation system for the prediction of the behavior of the pontoon type floating body supported by mooring dolphin in tsunami. In present simulation system, the 3D-MPS method is applied, and the solitary wave and the bore like wave are applied as a assumed tsunami. The present paper is a report of the first stage of the research, and the heaving motion on floating body in the tsunami is paid to attention, and it reports on the result of examining the detaching from mooring dolphin of floating body.

Behavior of a Pontoon Supported by a Mooring Dolphin in a Tsunami (First Report)

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mitsuhiro Masuda ◽  
Koichi Masuda ◽  
Tomoki Ikoma ◽  
Kuniaki Shoji
Keyword(s):  
Tsunami Wave ◽  
Container Terminal ◽  
Three Dimensional ◽  
Simulation System ◽  
Floating Body ◽  
Disaster Prevention ◽  
Floating Structure ◽  
Marine Disaster ◽  
Moving Particle ◽  
Present Simulation

In recent years, a number of floating facilities for the utilization of ocean space, such as a marine disaster prevention base, floating restaurant, or floating container terminal, are planned, and some of them are actually built. Most of these facilities are of the pontoon-type floating structure, and the mooring system is basically a mooring dolphin. In the design of such facilities, it is important that the prediction of the motions of a pontoon-type floating body, supported by a mooring dolphin, in a tsunami is obtained. The objective of the present research is to develop a simulation system to obtain such predictions. In the present simulation system developed here, the three-dimensional (3D) MPS method (moving particle semi-implicit method) is used, and a solitary wave and borelike wave are applied to represent the incoming tsunami wave. The present paper is a report of the first stage of the research, and the heaving motion of the floating body acted upon by the tsunami is paid special attention, and we also report on the results of the study of the detaching of the floating body from the mooring dolphin.

scholarly journals A Literature Review of Wave-Induced Heave Motion of Floating Structures

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Jia qi Xue
Keyword(s):  
Wave Theory ◽  
Body Motion ◽  
Irregular Waves ◽  
Floating Body ◽  
Superposition Method ◽  
Regular Waves ◽  
Floating Structure ◽  
Floating Structures ◽  
Heave Motion ◽  
Wave Induced

This paper provides comprehensive review on heave motion of rigid floating structure due to wave impacts. To specify and explain the structure response, this review firstly provides a brief introduction on ocean sea wave theory, floating structure motion interpretation. Then the floating body motion in regular waves was demonstrated using a superposition method of the oscillated motion in still water and the restrained motion in waves. Meanwhile, added mass and damping coefficient, these two frequency-dependent terms are brought into discussion to generate the motion response with given wave amplitude, which is known for response amplitude operator( RAO). Based on the study in regular waves, RAO of floating structure in irregular waves is introduced while no longer in time domain but in frequency domain. The whole review covers the literatures from the early 1980s up to nowadays, based on the review, it is recommended that more experimental work regarding to frequency characteristic and relative response of larger floating body should be carried out to improve the accuracy of this method.

Theory of Short Wave Excitation

1986 ◽  
Vol 30 (03) ◽  
pp. 147-152
Author(s):  
Yong Kwun Chung
Keyword(s):  
Incident Wave ◽  
Characteristic Length ◽  
Finite Depth ◽  
Short Wave ◽  
The Body ◽  
Wave Number ◽  
Floating Body ◽  
Wave Excitation ◽  
Exciting Forces ◽  
Wave Exciting Forces

When the wavelength of the incident wave is short, the total surface potential on a floating body is found to be 2∅ i & O (m-l∅ i) on the lit surface and O (m-l∅ j) on the shadow surface where ~b i is the potential of the incident wave and m the wave number in water of finite depth. The present approximation for wave exciting forces and moments is reasonably good up to X/L ∅ 1 where h is the wavelength and L the characteristic length of the body.

Extreme Response of Very Large Floating Structure Considering Second-Order Hydroelastic Effects in Multidirectional Irregular Waves

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Xujun Chen ◽  
Torgeir Moan ◽  
Shixiao Fu
Keyword(s):  
Second Order ◽  
Irregular Waves ◽  
Bending Moments ◽  
Floating Structure ◽  
First Order ◽  
Fluid Forces ◽  
Principal Coordinates ◽  
Vertical Displacements ◽  
Exciting Forces ◽  
Nonlinear Fluid

Hydroelasticity theory, considering the second-order fluid forces induced by the coupling of first-order wave potentials, is introduced briefly in this paper. Based on the numerical results of second-order principal coordinates induced by the difference-frequency and sum-frequency fluid forces in multidirectional irregular waves, the bending moments, as well as the vertical displacements of a floating plate used as a numerical example are obtained in an efficient manner. As the phase angle components of the multidirectional waves are random variables, the principal coordinates, the vertical displacements, and the bending moments are all random variables. Extreme values of bending moments are predicted on the basis of the theory of stationary stochastic processes. The predicted linear and nonlinear results of bending moments show that the influences of nonlinear fluid forces are different not only for the different wave phase angles, but also for the different incident wave angles. In the example very large floating structure (VLFS) considered in this paper, the influence of nonlinear fluid force on the predicted extreme bending moment may be as large as 22% of the linear wave exciting forces. For an elastic body with large rigidity, the influence of nonlinear fluid force on the responses may be larger than the first-order exciting forces and should be considered in the hydroelastic analysis.

scholarly journals Wave Exciting Forces on Groups of Floating Bodies

1979 ◽  
Vol 1979 (145) ◽  
pp. 79-87 ◽  
Author(s):  
Akira Masumoto ◽  
Yoshio Yamagami ◽  
Ryuji Sakata
Keyword(s):  
Floating Bodies ◽  
Exciting Forces ◽  
Wave Exciting Forces

scholarly journals Viscous-flow-based investigation of Cloaking phenomenon among multi-floating bodies and experimental verification

2019 ◽  
Vol 272 ◽  
pp. 01016
Author(s):  
Z K Wang ◽  
G H He ◽  
Z G Zhang ◽  
Y H Meng
Keyword(s):  
Experimental Research ◽  
Scattered Wave ◽  
Floating Body ◽  
Offshore Platforms ◽  
Floating Bodies ◽  
Cfd Simulations ◽  
Wave Drift ◽  
Real Coded Genetic Algorithm ◽  
Drift Force ◽  
Interaction Problem

The safety of mooring systems on offshore platforms seems more and more significant with the utilization of offshore space and resources, so the reduction of wave drift force is the key issue in this wave-body interaction problem. The wave drift force acting on the inner floating body surrounded by multiple small floating bodies can be reduced obviously with the occurrence of a phenomenon, which is called the Cloaking phenomenon. The Cloaking phenomenon refers to the reduction or complete elimination in amplitude of the scattered waves. In this paper, a real-coded genetic algorithm was used to optimize the parameters of outer floating bodies to minimize the scattered wave energy, and then the wave drift force acting on the inner body can be reduced. Furthermore, associated CFD simulations and experimental research were conducted with the above optimized parameters to investigate and verify the Cloaking phenomenon more systemically. It is shown that the wave drift force acting on the inner floating body in the Cloaking configuration can be reduced obviously both in numerical and experimental research, and the reduction of the wave drift force is closely related to the change of wave field around the structure.

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