• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.257-263
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• 2013

In this study, dynamic behaviors of a wave energy generation system (WEGS) that converts wave energy into electric energy are analyzed using multibody dynamics techniques. Many studies have focused on reducing the effects of a mooring system on the motion of a WEGS. Several kinematic constraints and force elements are employed in the modeling stage. Three-dimensional wave load equations are used to implement wave loads. The dynamic behaviors of a WEGS are analyzed under several wave conditions by using MSC/ADAMS, and the rotating speed of the generating shaft is investigated for predicting the electricity capacity. The dynamic behaviors of a WEGS with a mooring system are compared with those of a WEGS without a mooring system. Stability evaluation of a WEGS is carried out through simulation under extreme wave load.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.2
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• pp.193-201
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• 2014

The sea cage in marine aquaculture might be varied such as on the stability and shape in the open sea by environmental factors. To evaluate the stability of net cage structures in the open sea, the physical and numerical modeling techniques were applied and compared with field observations. This study was carried out to analyse the stability and the volume loss which would have an effect on the fish swimming behavior in the octagonal pillar type fish cage under the open sea. As a results, the volume loss ratio of the fish cage as measured using a depth sensor was indicated a value of the 30.3% under the current velocity (1.1m/s). The fish cage should be consisted of a concrete block with a weight over 10 tons, a mooring rope diameter over 28mm PP, and a shackle of 25mm under the current speed of 1m/sec for reasonable stability.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.1
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• pp.35-48
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• 1995

To develop the optimal design method for the longline type scallop culturing facilities in the open sea numerical calculations and hydraulic model experiments are carried out for the stability and function optimization. Using the results for the motion and tension of the facilities, stable design concepts and effects of motion control system by vertical anchor and resistance discs art discussed. The results of this study that can be applied to the design are as follows: 1) Total external forces by design wave $(H_{1/3}\;=\;6,7\;m,\;T_{1/3}\;=\;12sec)$ at the coastal waters of Jumunjin for unit facility (one main line) are estimated to 5-20 tons, and required anchor weights are 10-40 tons in the case of 2-point mooring system. Though the present facilities are stable to steady currents, but is unstable to the extreme wave condition of return period of 10 years. 2) The dimensions and depth of array systems must be designed considering the ecological environments as well as the physical characteristics including the mooring and holding forces that are proportional to the length and relative depth of main line to wave length, and the number of buoys and nets. 3) Oscillation of the facility is influenced by water particle motion and the weight of hanging net, and is excited at both edge, especially at the lee side. To reduce the motion of the nets, the vertical anchoring system and the resistence disc method are recommended by the experimental results, 4) The damage of rope near the anchor by abrasion should be prevented using the ring-type connection parts or anchor chains.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.427-432
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• 2018

Tidal current power is one of the energy sources of the ocean. Electricity can be generated by converting the flow energy of the current into the rotational energy of a turbine. Unlike tidal barrage, tidal current power does not require dams, which have a severe environmental impact. A floating-type tidal current power device can reduce the expensive support and installation cost, which usually account for approximately 41% of the total cost. It can also be deployed in relatively deep water using tensioned wires. The dynamic behavior of a floater and turbine force are coupled because the thrust and moment of the turbine affect the floater excursion, and the motion of the floater can affect the incoming speed of the flow into the turbine. To maximize the power generation and stabilize the system, the coupled motion of the floater and turbine must be extensively analyzed. However, unlike pile-fixed devices, there have been few studies involving the motion analysis of a moored-type tidal current power device. In this study, the commercial program OrcaFlex 10.1a was used for a time domain motion analysis. In addition, in-house code was used for an iterative calculation to solve the coupled problems. As a result, it was found that the maximum mooring load of 200 kN and the floater excursion of 5.5 m were increased by the turbine effect. The load that occurred on the mooring system satisfied the safety factor of 1.67 suggested by API. The optimum mooring system for the floating tidal current power device was suggested to maximize the power generation and stability of the floater.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.108-113
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• 2004

Marinas are often located in prime port side locations. hi Korea these locations are already developed and reclamation of the existing properties poses many difficulties and financial overhead. Also, to develop a standard marina in Korea with tide ranges up to 6 meters would require considerable dredging and reclamation works needing long lead times and large SOC costs. The Ocean Space's floating marina system is an independent offshore floating static level system that does not require fixed location breakwaters. The entire marina floats with the tide giving a calm consistent berthing condition for vessels irrespective of the surrounding tide and weather conditions. The floating marina system provides also for all of functions needed to marina comprising a breakwater to protect the vessels, the pontoon system to house the vessels, a dub house and retail tourism precinct, fuel reservoir and associated support facilities in a turn key self contained unit. The modular nature of the system will mean that initial demand can be met with simple units and then further modules can be added quite easily without the related expansion difficulties or infrastructure. This paper contains the main characteristics of the floating marina system and tire design process of the structure. The mooring, motion & stability analysis, the overall & local structural design and the mooring & anchor system design are introduced in this paper.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.3
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• pp.273-279
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• 2012

The concept of the Mobile Harbor had been made recently as a kind of feeder vehicle to transfer a certain amount of container boxes (i.e. 250 TEU at a time) from main ocean container vessels over 5,000 TEU capacity to the container terminal on land. In a harbor a short distance apart from the land, the container loading/unloading operation has to be performed on the main deck of the Mobile Harbor using the container cranes in the state of side-by-side mooring with protection of fenders and robot arms in the gap. Even under the ocean condition of the sea state class 2 or 3, the operation has to be confirmed to be safely performed. In this situation, the floating bodies considering the multiple-body interaction effect also has to be examined whether they might behave safely or not. Especially, this study focuses on the dynamic behavior of the Mobile harbor when a container box is hanged on the crane and the impact load due to the slewing motion is imposed in a certain sea state. The motion response should be controlled within the motion level to assure the safe operation.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.8-13
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• 2013

Excessive yaw motion of a turret moored vessel was examined in this paper. The vessel was moored by an internal turret and catenary mooring lines. The experiments were conducted in regular waves. Turret moored vessel can oscillate from side to side or move to one particular direction, and eventually exhibit large yaw motion. The results showed that the excessive yaw occured for specific condition, ratio of wave lengths and vessel length. It was found that turret moored floating vessel was unstable for regular wave period from 14 to 18 sec and excessive yaw occurred to maximum 50 deg. The time series, trajectory, phase plot and qualitative analysis are performed. The analysis showed that the results of experiments agreed with the that of analytic method and the excessive yaw could be predicted by the stability analysis.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.66-74
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• 2012

In this paper, the authors propose a new approach to control a barge type surface vessel. It is based on the Dynamic Positioning System(DPS) design. The main role of barge ship is to carry and supply the materials to the floating units and other places. To carry out this job, it should be positioned in the specified area. However sometimes the thrust systems are installed on it, and in general the rope control by mooring winch system is used. It may be difficult to compare the control performances of two types. If we consider this problem in point of usefulness, we can easily find out that the winch control system is more useful and applicable to the real field than the thrust control system except a special use. Therefore, in this paper we consider a DPS design problem which can be extended to the many application fields. The goal of this paper is twofold. First, the sliding mode controller (SMC) for positioning the our vessel is proposed. Especially, in this paper, a robust stability condition is given based on descriptor system representation. In the result, the sliding mode control law guarantees to keep the vessel in the defined area in the presence of environmental disturbances. And second, the thrust allocation problem is solved by using redistributed pseudo-inverse (RPI) algorithm to determine the thrust force and direction of each individual actuator. The proposed approach has been simulated with a supply vessel model and found work well.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.1
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• pp.1-8
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• 2014

Pultruded glass fiber reinforced polymeric plastic (PFRP) and FRP member manufactured by sheet molding compound (SMC) have superior mechanical and physical properties compared with those of conventional structural materials. Since FRP has an excellent corrosion-resistance and high specific strength and stiffness, the FRP material may be highly appreciated for the development of floating-type photovoltaic (PV) power generation system. In this paper, advanced floating PV generation system made of PFRP and SMC is designed. In the design, it includes tracking solar altitude by tilting photovoltaic arrays and tracking solar azimuth by spinning structures. Moreover, the results of the finite element analysis (FEA) are presented to confirm stability of entire structure under the external loads. Additionally, installation procedure and mooring systems in the Hap-Cheon Dam are discussed and the measurement of strain under the actual circumstances is conducted for assuring stability of actually installed structures. Finally, by comparison with allowable stress, appropriate safety of structure is confirmed to operate the system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.407-416
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• 2023

Demand for leisure facilities such as mooring facilities for berthing leisure vessels and floating pensions based on floating bodies is increasing owing to the rapid growth of the population and related industries for marine leisure activities. Owing to its relatively light weight as a fluid, inclination is easily generated by waves and surcharges flowing to the coast, resulting in frequent safety accidents because of the low stability. As a solution to this problem, a motion reduction device for floating bodies is proposed in this study. The device (motion reduction device based on the air pressure dif erence) was attached to a floating body and the effect was analyzed by comparing the results with those of a floating body without motion reduction. The effect analysis was further analyzed using a computer analysis test, and the method for increasing the stability of the floating body was studied, and its the effect was verified. Based on the analysis of the test results, the stability of the floating body increased with a motion damping device is higher than that of the floating body without a motion reducing device as the wave momentum reduces, owing to the air pressure difference. Therefore it was concluded that the use of such a device for reducing motion a floating body is useful not only for non-powered ships but also for powered and semi-submersible ships, and further research should be conducted by applying it to various fields.