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

1999 ◽  
Vol 1999 (186) ◽  
pp. 235-242 ◽  
Author(s):  
Yasuhiro Namba ◽  
Syunji Kato ◽  
Masakatu Saito
Keyword(s):  
Estimation Method ◽  
Floating Structures ◽  
Wave Drift ◽  
Drift Force ◽  
Very Large Floating Structures

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

Response of the Mega-Float Equipped With Novel Wave Energy Absorber

2003 ◽  
Author(s):  
Sotaro Masanobu ◽  
Shunji Kato ◽  
Katsuya Maeda ◽  
Yasuhiro Namba
Keyword(s):  
Wave Energy ◽  
Structural Design ◽  
Estimation Method ◽  
The Novel ◽  
Additional Structure ◽  
Energy Absorber ◽  
General Wave ◽  
Wave Drift ◽  
Drift Force ◽  
Hydroelastic Response

The hydroelastic response is significant from the viewpoint of the structural design of a Mega-Float. Equipping a Mega-Float with some additional structures, such as vertical plates, is one of the ways to reduce the hydroelastic response easily. However, in general, wave drift force acting on the Mega-Float may be increased, when the Mega-Float is equipped with the additional structures to reduce the response. In the present study, we developed a novel additional structure that was effective in the reduction of both hydroelastic response and wave drift force. Furthermore, we estimated the response of Mega-Float equipped with the additional structures, and compared the result with the value measured in at-sea experiments. As a result, we confirmed both the effectiveness of the novel additional structure and the validity of the estimation method.

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.

Mean Wave Drift Force on a Barge-Type Floating Wind Turbine With Moonpools

2021 ◽  
Author(s):  
Lei Tan ◽  
Tomoki Ikoma ◽  
Yasuhiro Aida ◽  
Koichi Masuda
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Hydrodynamic Performance ◽  
Vertical Axis Wind Turbine ◽  
Rotating Speed ◽  
Wave Drift ◽  
Floating Offshore Wind Turbines ◽  
Drift Force ◽  
Gyroscopic Effects

Abstract The barge-type foundation with moonpool(s) is a promising type of platform for floating offshore wind turbines, since the moonpool(s) could improve the hydrodynamic performance at particular frequencies and reduce the costs of construction. In this paper, the horizontal mean drift force and yaw drift moment of a barge-type platform with four moonpools are numerically and experimentally investigated. Physical model tests are carried out in a wave tank, where a 2MW vertical-axis wind turbine is modelled in the 1:100 scale. By varying the rotating speed of the turbine and the mass of the blades, the gyroscopic effects due to turbine rotations on the mean drift forces are experimentally examined. The wave diffraction and radiation code WAMIT is used to carry out numerical analysis of wave drift force and moment. The experimental results indicate that the influence of the rotations of a vertical-axis wind turbine on the sway drift force is generally not very significant. The predictions by WAMIT are in reasonable agreement with the measured data. Numerical results demonstrate that the horizontal mean drift force and yaw drift moment at certain frequencies could be reduced by moonpool(s).

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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