Mitsuhiro Masuda

Behavior of a Pontoon Supported by a Mooring Dolphin in a Tsunami (First Report)

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.

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

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

A Fundamental Research on the Effects of a Floating Berth on Reduction of Tsunami Damages in a Harbor: Reduction Effects of the Breaking of Mooring Lines and Running on a Quay

Tsunami consecutively brings about several types of disasters, which is described as “disaster chain.” In the case that vessels are moored to the quay, the breaking of the mooring line possibly causes drift or collision with other vessels. There is also a case that a mooring tether of the vessel moored to the floating pier is not broken in the damage of tsunami, which was confirmed at Shiogama port in Miyagi when the East Japan Great Earthquake occurred on March 11, 2011.The objectives of this paper are to clarify the reduction effect of mooring line force when a vessel is moored to a floating berth. The three-dimensional MPS method is used with advantages of floating berth considered. We simulated a vessel with the cargo carrier of 3,000t. Especially, by changing the wave elevation and the incident angle, the responses of the mooring tension which acts on the vessel moored to a floating berth and to the quay respectively are compared, and its reducing efficiency is examined. A conclusion is reached that, when tsunami incident wave angle is 90 degrees, mooring vessels to a floating berth can be expected as a solution to reduce the problems of vessel’s running onto a quay, in comparison with mooring them at a quay wall. Also, we propose suitable anchoring methods according to the size of the vessels.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

Fundamental Research on the Behaviors of Floating Vessels Moored to Floating Piers in Tsunami

Tsunami disasters of floating vessels moored to a quay are complex, such as breaking of the mooring lines and then drifting and collision of floating vessels. There was an example in which a mooring tether of a ship moored to a floating pier did not break in the damage of tsunami. This was confirmed in Shiogama Harbor in Miyagi Prefecture during the East Japan great earthquake which occurred on March 11, 2011. The objectives of this paper are to clarify the effect of reducing mooring tether force in the case of a ship moored to a floating pier, by means of the 3D-MPS method, as well as the advantages of a floating pier for a fixed mooring quay. In addition, in this paper the authors discuss the following items: 1) force of a tsunami wave on the piles of a floating pier; and 2) response characteristics for various incidence angles. Also, we propose measures to prevent drift of a floating pier in tsunami. Finally, these results are used for development of a floating pier for prevention of a vessel being washed away by tsunami.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