Study on Influence of Geometrical Dimensions of Floating Bodies on Cloaking Phenomenon

2016 ◽  
Author(s):  
Zhigang Zhang ◽  
Guanghua He ◽  
Xiaoqun Ju ◽  
Dong Yu
Keyword(s):  
Wave Interaction ◽  
Floating Body ◽  
Geometrical Parameters ◽  
Offshore Platforms ◽  
Ocean Engineering ◽  
Floating Bodies ◽  
Floating Structures ◽  
Wave Drift ◽  
Drift Force ◽  
Geometrical Dimensions

Mooring offshore floating structures such as offshore platforms in large waves and winds, against the drift force and rotational moments are challenging in offshore engineering and ocean engineering. To investigate these kind of problems named positioning problems accurately, not only in hydrodynamic forces of first order but also in time-averaged steady forces of second order named wave drift force need to be taken into account. That arranging of several small cylinders regularly on a circle concentric with a fixed floating body is considered to reduce the wave drift force. Fortunately, a Cloaking phenomenon occurs at certain conditions with proper geometrical dimensions of floating bodies, which can reduce the wave drift force acting on bodies, perfectly even to zero. In this paper, with a combination of higher-order boundary element method (HOBEM) and wave-interaction theory, the influences of geometrical parameters of outer surrounding cylinders on the wave drift force of floating bodies are systematically investigated and discussed.

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.

scholarly journals Estimation method of slowly varying wave drift force acting on very large floating structures

2000 ◽  
Vol 2000 (188) ◽  
pp. 287-293
Author(s):  
Yasuhiro Namba ◽  
Shunji Kato ◽  
Hiroshi Sato ◽  
Tomoki Ikoma ◽  
Katsuya Maeda
Keyword(s):  
Estimation Method ◽  
Floating Structures ◽  
Wave Drift ◽  
Drift Force ◽  
Very Large Floating Structures

Nonlinear impulse of ocean waves on floating bodies

2012 ◽  
Vol 697 ◽  
pp. 316-335 ◽  
Author(s):  
Paul D. Sclavounos
Keyword(s):  
Time Derivative ◽  
Ocean Waves ◽  
The Body ◽  
Offshore Wind ◽  
Floating Body ◽  
Offshore Platforms ◽  
Wave Loads ◽  
Floating Bodies ◽  
Bernoulli’S Equation ◽  
Hydrostatic Force

AbstractA new formulation is presented of the nonlinear loads exerted on floating bodies by steep irregular surface waves. The forces and moments are expressed in terms of the time derivative of the fluid impulse which circumvents the time-consuming computation of the temporal and spatial derivatives in Bernoulli’s equation. The nonlinear hydrostatic force on a floating body is shown to point vertically upwards and the nonlinear Froude–Krylov force and moment are derived as the time derivative of an impulse that involves the time derivative of a simple integral of the ambient velocity potential over the time-dependent body wetted surface. The nonlinear radiation and diffraction forces and moments are expressed as time derivatives of two impulses, a body impulse and a free surface impulse that represents higher-order wave loads acting along the body waterline. Numerical results are presented illustrating the accuracy of the new force expressions. Applications discussed include the nonlinear seakeeping of ships and offshore platforms and the extreme wave loads and responses of offshore wind turbines.

Nonlinear Hydrodynamic Forces on an Accelerated Body in Waves

2005 ◽  
Vol 127 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Motoki Yoshida ◽  
Takeshi Kinoshita ◽  
Weiguang Bao
Keyword(s):  
Perturbation Analysis ◽  
Low Frequency ◽  
Multiple Scale ◽  
Added Mass ◽  
Floating Body ◽  
Floating Bodies ◽  
Low Frequency Oscillations ◽  
Wave Drift ◽  
Decay Test ◽  
Field Radiation

Wave-drift added mass results from nonlinear interactions between waves and low-frequency oscillatory motions of a floating body, in the presence of incident waves. In previous works, wave-drift damping which is the component of wave-drift force in phase with the velocity of low-frequency oscillations was investigated mainly based on a quasi-steady analysis. However, investigations related to wave-drift added mass, the component in phase with acceleration, were very few. In this paper, wave-drift added mass is derived directly from a perturbation analysis with two small parameters and two time scales, using a Cartesian coordinate system that follows the low-frequency oscillations, dynamic oscillation model has been used. Especially, the method to solve higher-order potentials, which are necessary for evaluation of wave-drift added mass, is presented. Analytical solutions and calculated results of wave-drift added mass, and far field radiation conditions for each order of potentials are obtained. Also, wave-drift added mass of floating bodies has been systematically measured from a slowly forced oscillation test or a free decay test in waves. Experimental results are compared with calculated results. Then, for a supplement, the secular behavior that some velocity potentials show is discussed. Applying a multiple scale perturbation analysis to one of these problems, a nonsecular solution is obtained.

Reciprocal Form of the Wave Drift Force and Moment Acting on Floating Body

2008 ◽  
Author(s):  
Takashi Tsubogo
Keyword(s):  
Body Surface ◽  
Near Field ◽  
Floating Body ◽  
Far Field ◽  
Regular Waves ◽  
Momentum Theory ◽  
Wave Drift ◽  
Drift Force

This paper provides the reciprocal form on wave drift force and moment from the momentum theory. The author in Japan has transformed from the pressure integration on the wetted body surface oscillating in regular waves into the reciprocal form at the near field, then transformed into the form at the far field owing to Green’s second identity, and transformed into Maruo’s and Newman’s formulas. But in this paper the start point is the momentum theory and the goal is the reciprocal form. The obtained reciprocal form at the far field can be transformed into the integration over the wetted floating body surface owing to Green’s second identity.

Study on Collision Forces on Water-Front Facilities Induced by Floating Vessels Washed Onto Apron by Tsunami

2010 ◽  
Author(s):  
Koichi Masuda ◽  
Mitsuhiro Masuda ◽  
Tomoki Ikoma
Keyword(s):  
Numerical Simulation ◽  
Floating Body ◽  
Present Calculation ◽  
Floating Bodies ◽  
Floating Structures ◽  
Mps Method ◽  
Calculation Results ◽  
Moving Particle ◽  
Collision Force ◽  
Water Front

The present paper describes the application of the moving particle semi-implicit method to a prediction of collision forces on water-front facilities induced by floating vessels washed onto the apron by tsunami. Effectiveness of the application is verified. Solitary waves are applied to simulated tsunamis in numerical simulation and to the model experiments. A pontoon type floating body is applied to floating structures in numerical simulations using the MPS method. The present calculation results are compared with the experimental results and the applicability of MPS method is discussed. Further, after being washed onto the wharf by tsunami, the characteristics of collision force on water-front facilities induced by the floating bodies are discussed.

A quasi-cloaking phenomenon to reduce the wave drift force on an array of adjacent floating bodies

2018 ◽  
Vol 71 ◽  
pp. 1-10 ◽  
Author(s):  
Zhigang Zhang ◽  
Guanghua He ◽  
Masashi Kashiwagi ◽  
Zhengke Wang
Keyword(s):  
Floating Bodies ◽  
Wave Drift ◽  
Drift Force

scholarly journals Experimental and Numerical Analysis of Wave Drift Force on KVLCC2 Moving in Oblique Waves

2021 ◽  
Vol 9 (2) ◽  
pp. 136
Author(s):  
Min Guk Seo ◽  
Yoon Jin Ha ◽  
Bo Woo Nam ◽  
Yeongyu Kim
Keyword(s):  
Numerical Analysis ◽  
Ocean Engineering ◽  
Validation Data ◽  
Wave Drift ◽  
Motion Responses ◽  
Direct Pressure ◽  
Korea Research Institute ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

In this study, experimental and numerical methods were applied to estimate surge and sway wave drift forces and yaw drift moment acting on KVLCC2, advancing in oblique wave. An experiment was carried out in the ocean engineering basin of the Korea Research Institute of Ships and Ocean Engineering (KRISO). A series of regular wave tests under various heading conditions were conducted to investigate ship motion responses and wave drift forces. A Rankine panel method based on potential flow was adopted in the numerical analysis, and the direct pressure integration method that integrates second-order pressure on the hull surface was applied to compute wave drift force. Through this study, validation data of wave drift force acting on KVLCC2 was established, and the computation capability of the potential-based numerical method was systematically analyzed.

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