Numerical Simulation of Ocean Environmental Change Due to Very Large Offshore Structures in a Bay

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Fundamental studies on ocean environmental changes due to a huge offshore structure are carried out in this project. An offshore airport in Ariake Bay is taken as an example and tidal simulations are conducted in the bay with/without the offshore airport. The deffusion simulations of COD from rivers are also conducted and the results of COD density patterns are compared. In tidal simulations, the moving effects of water on the tidal marsh are taken into account by the quasi-stastic approximation. In 1993, three location of a reclaimed airport and a simplified floating airport are compared in assessment functions which are defined by the area affected in tidal level and current velocity by the construction of the airport. The location of the airport is found to be very important in the tidal currents and deffusion of COD in the bay. In 1994, a new numerical program is developed for a pontoon type floating airport. Results of a floating airport show that it gives less effects on ocean en … More vironmental changes than reclaimed airports.A dynamic positioning system of a mooed floating platform is studied. Mooring is used to maintain the position of a floating platform against quasi-constant external forces induced by current and wind, and thrusters control slow drift oscillation. The LQI (Linear Quadratic with Integral) control system was adopted to prevent this oscillation.Simulations of motions in irregulay waves, currents and wind were carried out and the performance of LQI control system was presented.The wave drifting forces acting on a very large floating structure consisting of multiple barge type modules is studied theoretically and experimentally. The wave drifting forces on the multiple floating structure are estimated for two module connectors, a rotationally-hinge connector and a rotationlly-rigid connector. The effects of connector conditions and the number of bodies on wave drifting forces are presented graphically.A new method for computation of the hydrodynamic forces acting on a floating body in a harbor of arbitrary geometry is developed. The method is composed of the finite element method (FEM) for solving the harbor response and the boundary element method (BEM) for the floating body response. Some numerical results are presented for a barge in a rectangular harbor. Less