Kiyokazu Minami

A Study on Development of the Performance Analysis Method of the Floating OWC-WEC Using the MPS Method

When concrete examination towards utilization is needed, it is necessary to estimate the safety and the performance of a floating Oscillation Water Column (OWC)-type wave energy converter under abnormal oceanographic phenomenon such as large waves, wave impact force, deck wetness and complex motion of mooring system. Therefore, to choose a proper numerical method is important. This present paper describes a fundamental study about estimation of safety and performance of floating OWC-type wave energy converter using the two-phase flow MPS method. In this research, firstly, new algorithm is installed in order to solve problems of the two-phase flow MPS method. Secondly, applicability to an response analysis of a wharf installation type OWC-WEC of the improved MPS method is examined by wave pressure acting to the OWC-WEC and response in the air chamber of the OWC-WEC.Copyright

Increasing ship roll stability by using anti-rolling tanks

This paper shows a study on anti-rolling tank and its effects on ship roll motion. A flexible passive anti-rolling tank that consists of two fixed reservoirs, a set of three connected ducts and a set of five connected air pipes is designed for carrying out experiments. Experiments were conducted in regular sinusoidal waves of small amplitude and in irregular waves. First step, experiments are conducted in regular waves. Second step, experiments are conducted in irregular waves. For regular wave, experiments were conducted in constant wave heights and constant wave slopes. For irregular wave, experiments were conducted in two idealized wave spectrum. Those spectrum are ITTC (International Towing Tank Conference) idealized spectrum and JONSWAP (Joint North Sea Wave Project) idealized spectrum. After carrying out experiments and analysis, a view of the effects of the designed anti-rolling tank on roll motion of the model ship is shown in this paper. Both theoretical and experimental results show that when the model ship using the anti-rolling tank, the roll stability of the model ship is increased. It is recognized that the highest effects of anti-rolling tank on roll motion of the model ship in experiments with both regular waves and irregular waves are obtained when the model ship is experimented with a wave frequency nearby its natural roll frequency. At this level of the water, the natural frequency of the anti-rolling tank is also nearby the natural roll frequency of the model ship.

A Fundamental Study on the Applicability of the Floating Large Size Tsunami Shelter

A floating large-size tsunami shelter (FLTS) has been proposed. The shelter can evacuate more than 1500 people to evacuate from run-up tsunami. The floating tsunami shelter can be lifted by buoyancy when tsunami hitting. In this study, First, Authors assumed Principal specifications of the FLTS from estimation of damage and second we evaluated the validity and safety of a floating large size tsunami shelter using the mooring dolphin by water tank experiment and numerical simulation that is moving particle semi-implicit method (MPS). As a result, enough performance was recognized. The mooring of dolphin was reduced the motion against 10m height tsunami than no moored. However it became clear about the numerical simulation that improvement was more necessary. In particular, the collision model was necessary improved by the existing model.Copyright

On Optimal Method of Mooring Ship in Floating Tsunami Protection Wharf

On the vessels moored the quay, the situation such as drifting and runs on the quay due to the breaking of the mooring lines is generated by the tsunami. The authors are clarified for applicability of the proposed floating tsunami protection wharf (FTPW) and install more mooring tether. The effect of FTPW is most promising as disaster prevention and mitigation measures for the vessels moored quay, but exert a sufficient effect in the transverse tsunami incident, but the effect cannot be confirmed in the longitudinal tsunami incident. Therefore, it is necessary to go in combination in FTPW and tsunami countermeasures in consideration of the longitudinal tsunami incident, such as install more mooring tether and new mooring method. The objectives of present study are to consider valid mooring method for longitudinal tsunami incident and also to propose a tsunami most effective countermeasure of wharf mooring vessel.Copyright

A Fundamental Study on Anchor Performance Evaluation for Marine Accident Prevention

From the viewpoint of prevention of the accident of ships under anchorage, an anchor is a very important device. The anchor with various types and performances has been developed over the centuries. For example, JIS types and AC-14 types are mostly applied to Japanese ships at present. However, marine accidents by dredging anchor are not eliminated even now. There still seems a room for improvement of its performance by changing shapes and forms. There may be a problem also in the experiment method and a valuation method. The purpose of this research is to perform an anchor performance re-evaluation for marine accident prevention. The candidates for an experiment are JIS type, AC-14 type, DA-1 type stockless anchor and Danforth type stock anchors.Copyright

Study on Development of the Floating Pier for Damage Protection Control of Ship in Tsunami

When the tsunami attacks in harbors, the vessels moored at the wharf may be unable to be evacuated. In such a case, damages such as, breaking the mooring tethers, grounding on a wharf, drift to land areas and the collision with buildings are assumed. And, after suffering a disaster, the base for supporting medical treatment and a life is necessary to disaster victims. In this research, the floating tsunami protection wharf (FTPW) is proposed. This present paper describes the tsunami simulation and the motion analysis of vessel moored at the FTPW using the MPS Method. In this research, the 3D-MPS method is applied. The applicability of the FTPW was examined. Moreover, the feasibility of the disaster victim support base on the FTPW deck was examined.Copyright

A Fundamental Study on Tsunami Damage Control of Moored Vessels Using the MPS Method

When the tsunami attacks in harbors, the vessels moored at the wharf may be unable to be evacuated. In such a case, damages such as, breaking the mooring tethers, grounding on a wharf, drift to land areas and the collision with buildings are assumed. This present paper describes the tsunami simulation and the motion analysis of vessel moored at the wharf using the MPS Method. In this research, the 3D-MPS method is applied. The chart of mooring tethers break was created. The wave height of tsunami and the relation of the break of the mooring tethers were shown by the chart of mooring tethers break. The chart was created about the influence of number of mooring tethers, diameter of mooring tethers and mooring system to the break of mooring tethers.Copyright

Simulation of the Mooring Vessels in Tsunamis Using the MPS Method Considers Leading Wave and Backwash

The present paper describes the simulation of behavior of mooring vessels in tsunami using the 3-D MPS (Moving Particle Semi-implicit) Method for considering leading wave and backwash effect. The chain of a disaster is brought about by two kinds of tsunami. The chain of disaster means breaking the mooring tether, grounding on a wharf, drift to continental areas, the collision with building by leading wave and the outflow of the floating matter by backwash. In this research, the 3D-MPS method is applied, and the bore like wave is applied as an assumed tsunami. The expression of backwash is tried by water pillar collapse. The present calculation results are compared with the experimental results and the applicability of the MPS method is discussed. In addition, the vehicle is arranged on a wharf, and the chain of disaster is simulated.Copyright

Responses of Roll Damping on Anti-rolling Tank Devices

This paper shows a study on roll damping of anti-rolling tank (ART). A flexible passive ART that consists of two fixed reservoirs, a set of three connected ducts and a set of five connected air pipes is designed for carrying out experiments. Experiments were conducted in regular sinusoidal waves of small amplitude. A view of the effect of designed ART on roll damping is shown in this research. To estimate roll damping coefficients of the model ship, several serials of experiments have been conducted. Experiments had been conducted with various diameters of the ducts and various numbers of opened valves of the connected air pipes. By changing the diameter of the ducts and controlling the number of opened valves of the connected air pipes, the volumes of moving water and air flows between two reservoirs will be changed. Consequently, the roll damping coefficients and the stabilizing moments of the ART are changed, too. Some graphs that show the responses of roll damping of the ART are drawn. The influence of the ART on roll damping of the model ship is compared in theory and in experiments. Both theoretical and experimental results show that when the model ship using ART, a stabilizing moment is created. This stabilizing moment will make the magnitude of roll motion of the model ship reduced. It is recognized that the highest effect of ART to roll motion of the model ship is obtained when the model ship is experimented with a wave frequency near its natural frequency.