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.

The Design and Calculation of the Mooring System in Floating Body with Rope Wheel Device

2013 ◽  
Vol 361-363 ◽  
pp. 378-381
Author(s):  
Yan Gang Wang ◽  
Xing Hua Tong ◽  
Lin Sen Zhu ◽  
Yong Liu
Keyword(s):  
Potential Energy ◽  
Wave Energy ◽  
Low Cost ◽  
Floating Body ◽  
Mooring System ◽  
New Wave ◽  
Floating Structure ◽  
Energy Device ◽  
Key Technology ◽  
Energy Theory

Floating body with rope wheel structure is a new wave energy device, which is simple and low cost. Mooring system is the key technology of this device, which is use to limit the horizontal motion of the floating structure in the designated area. In this paper, potential energy theory has been used in the process of design and calculation of mooring system. Using the result of calculation, the motion of the floating body has been simulated numerically.

A Hydrodynamic Analysis of Offshore Platform Based on the AQWA

2014 ◽  
Vol 615 ◽  
pp. 301-304 ◽  
Author(s):  
Shi Ming Wang ◽  
Bing Feng Shi ◽  
Zi Nan Lin ◽  
Wei Zou
Keyword(s):  
Power Generation ◽  
Offshore Platform ◽  
Floating Body ◽  
Mooring System ◽  
Land Resources ◽  
Hydrodynamic Analysis ◽  
Power Generation Equipment ◽  
Drying Up ◽  
Oil And Natural Gas ◽  
Floating Type

With the drying up of land resources, the oil and natural gas,power generation equipment, and ocean data is in so great request that the research of the offshore platform is increasingly important.Offshore platform structure and the design of the mooring system both are influenced by the hydrodynamic performance.Then the floating type marine equipment carrier of hydrodynamic being analyzed after doing the frequency domain calculation for the model of floating body by the hydrodynamic software AQWA here.

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.

North Sea Mooring Systems: How Reliable Are They?

2014 ◽  
Author(s):  
Will Brindley ◽  
Andrew P. Comley
Keyword(s):  
Continental Shelf ◽  
North Sea ◽  
Recent Decade ◽  
Mooring Line ◽  
Mooring System ◽  
Failure Rates ◽  
Floating Structure ◽  
Strength Capacity ◽  
Failure Statistics ◽  
Overall Reliability

In recent years a number of high profile mooring failures have emphasised the high risk nature of this element of a floating structure. Semi-submersible Mobile Offshore Drilling Units (MODUs) operating in the harsh North Sea environment have experienced approximately 3 mooring failures every 2 years, based on an average population of 34 units. In recognition of the high mooring failure rates, the HSE has introduced recommendations for more stringent mooring strength requirements for units operating on the UK Continental Shelf (UKCS) [17]. Although strength requirements are useful to assess the suitability of a mooring design, they do not provide an insight into the question: what is the reliability of the mooring system? This paper aims to answer this question by evaluating failure statistics over the most recent decade of available data. Mooring failure rates are compared between the Norwegian Continental Shelf (NCS), the UKCS, and with industry code targets to understand how overall reliability is related to the strength capacity of a mooring system. The failure statistics suggest that a typical MODU operating in the UKCS would experience a mooring line failure in heavy weather approximately every 20 operating years. This failure rate appears to be several orders of magnitude greater than industry targets used to calibrate mooring codes. Despite the increased strength requirements for the NCS, failure rates do not appear to be lower than the UKCS. This suggests that reliability does not correlate well with mooring system strength. As a result, designing to meet the more rigorous HSE requirements, which would require extensive upgrades to existing units, may not significantly increase mooring system reliability. This conclusion needs to be supported with further investigation of failure statistics in both the UKCS and NCS. In general, work remains to find practical ways to further understand past failures and so improve overall reliability.

RFID-Based Thermal Bubble Non-Floating Type Accelerometer with Semi-Cylindrical Chamber and Filled with Xenon Gas

2011 ◽  
Vol 317-319 ◽  
pp. 1153-1162
Author(s):  
Jium Ming Lin ◽  
Po Kuang Chang ◽  
Cheng Hung Lin ◽  
Qi Kun Zhang
Keyword(s):  
Carbon Dioxide ◽  
Molecular Weight ◽  
Response Time ◽  
Flexible Substrate ◽  
Thermal Sensors ◽  
Cylindrical Chamber ◽  
Floating Structure ◽  
Key Technology ◽  
Impact Condition ◽  
Floating Type

This research proposes a wireless RFID-based thermal bubble accelerometer design, and relates more particularly for the technology to manufacture and package it on a flexible substrate. The key technology is to integrate both a thermal bubble accelerometer and a wireless RFID antenna on the same substrate, such that the accelerometer is very convenient for fabrication and usage. In this paper the heaters as well as the thermal sensors are directly adhering on the surface of the flexible substrate without the traditional floating structure. Thus the structure is much simpler and cheaper for manufacturing, and much more reliable in large acceleration impact condition without broken. Furthermore, the molecular weight of xenon gas is much larger than carbon dioxide, thus the performance of the accelerometer will be increased. In addition, the shape of the chamber is changed as a semi-cylindrical one instead of the conventional rectangular type. Comparisons of sensitivity and response time are also made; one can see the performances of the proposed new design with either semi-cylindrical chamber or filled with xenon gas are better.

Effects of Disturbance of Current Field on Power Characteristics of a Floating Type Pitch-Controlled VAMT in a Real Sea

2016 ◽  
Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Hiroaki Eto ◽  
Chang-Kyu Rheem ◽  
Osamu Enomoto
Keyword(s):  
Fluid Velocity ◽  
Vertical Axis ◽  
Ocean Waves ◽  
Floating Body ◽  
Maximum Output ◽  
Power Characteristics ◽  
Turbine Performance ◽  
Velocity Changes ◽  
Floating Type ◽  
Japanese Islands

While a type of marine turbine for tidal current generation can be chosen from several types, a vertical axis marine turbine (VAMT) should be better in Japan because sea areas around Japanese islands where current velocity is sufficient are limited. This study conducted a sea test of a VAMT of a floating type installed with six straight pitch-controllable blades. The cycloidal mechanism was adapted for the pitch control. The purpose of the study is to understand effects of ocean waves and motion of a floating body on turbine performance and behaviours of the VAMT in unideal current conditions. Besides, the data taken should be effective to consider that effects in order to design VAMTs. The setup with the setting angle of −30 degrees suggested highest performance from the sea tests, then 15% in maximum turbine power and maximum output was 40W. Ocean waves strongly affected on the turbine performance because fluid velocity changes due to ocean waves and it was unable to neglect the variation of the velocity in spite of small. The characteristics of the turbine sensitively varied because of ocean waves. The results suggested that during accelerating and decelerating incoming fluid speed, characteristics of the turbine were different in each case.

Floating Offshore Wind Turbines: Responses in a Seastate Pareto Optimal Designs and Economic Assessment

2008 ◽  
Author(s):  
Paul Sclavounos ◽  
Christopher Tracy ◽  
Sungho Lee
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Wind Farms ◽  
Economic Assessment ◽  
Offshore Wind ◽  
Pareto Optimal ◽  
Mooring System ◽  
Floating Structure ◽  
Water Depths

Wind is the fastest growing renewable energy source, increasing at an annual rate of 25% with a worldwide installed capacity of 74 GW in 2007. The vast majority of wind power is generated from onshore wind farms. Their growth is however limited by the lack of inexpensive land near major population centers and the visual pollution caused by large wind turbines. Wind energy generated from offshore wind farms is the next frontier. Large sea areas with stronger and steadier winds are available for wind farm development and 5MW wind turbine towers located 20 miles from the coastline are invisible. Current offshore wind turbines are supported by monopoles driven into the seafloor at coastal sites a few miles from shore and in water depths of 10–15m. The primary impediment to their growth is visual pollution and the prohibitive cost of seafloor mounted monopoles in larger water depths. This paper presents a fully coupled dynamic analysis of floating wind turbines that enables a parametric design study of floating wind turbine concepts and mooring systems. Pareto optimal designs are presented that possess a favorable combination of nacelle acceleration, mooring system tension and displacement of the floating structure supporting a five megawatt wind turbine. All concepts are selected so that they float stably while in tow to the offshore wind farm site and prior to their connection to the mooring system. A fully coupled dynamic analysis is carried out of the wind turbine, floater and mooring system in wind and a sea state based on standard computer programs used by the offshore and wind industries. The results of the parametric study are designs that show Pareto fronts for mean square acceleration of the turbine versus key cost drivers for the offshore structure that include the weight of the floating structure and the static plus dynamic mooring line tension. Pareto optimal structures are generally either a narrow deep drafted spar, or a shallow drafted barge ballasted with concrete. The mooring systems include both tension leg and catenary mooring systems. In some of the designs, the RMS acceleration of the wind turbine nacelle can be as low as 0.03 g in a sea state with a significant wave height of ten meters and water depths of up to 200 meters. These structures meet design requirements while possessing a favorable combination of nacelle accleration, total mooring system tension and weight of the floating structure. Their economic assessment is also discussed drawing upon a recent financial analysis of a proposed offshore wind farm.

Experimental Study on Water Damping Effects of Hybrid Floating Structure

2013 ◽  
Author(s):  
Youn-Ju Jeong ◽  
Young-Jun You ◽  
Du-Ho Lee ◽  
Min-Su Park
Keyword(s):  
Natural Frequency ◽  
Hybrid Model ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Oscillation Period ◽  
Floating Body ◽  
Small Scale ◽  
Floating Structure ◽  
Damped System ◽  
Damping Effects

In this study, in order to evaluate water damping effects of hybrid pontoon system with cylinders, experimental studies were carried out. At first, in order to evaluate oscillatory motions, three small-scale models of hybrid, tapered, and pontoon were fabricated and tested under the still-water condition. Four acceleration gauges were attached on the top edges and acceleration of top edge were measured during the oscillation. Then, oscillatory motions of oscillation period and stabilizing time to steady-state were analyzed. Finally, based on the oscillatory motions, damping properties of the logarithmic decrement, damping ratio, and natural frequency of damped system were calculated and compared with each other. As the results of this study, it was found that hybrid model presented about 3.67 times higher decay rate of amplitude of the oscillatory motion than the pontoon model. Also, hybrid model presented about 3.67 times higher damping ratio than the pontoon model. Whereas the natural frequency of the pontoon and tapered model were nearly same with the natural frequency of undamped system, that of the hybrid model presented some difference with the that of the undamped system. In addition, periods of floating body at the wet mode presented about 1.5∼3.0 times longer periods than the dry mode, and it was expected that there was not possibility for the resonance. Therefore, it was expected that the hybrid model of this study should contribute to improve serviceability and safety of offshore floating structures as decreasing oscillatory motions.

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