RESEARCH ON PREDICTION & PREVENTION OF VIBRATION IN STRUCTURES IN CONTACT WITH WATER

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Large underwater shell structures can be used as LNG storage tanks and research laboratories for reserch on oceans. We have performed a part of feasibility study on such new structures in the future. The shape of the underwater shell structures is axisymmetric because of the strength against the hydrostatic pressure. Especially we focused on the dynamic characteristics of the structures under the sea because our country syfers from frequent erthquakes. We examined the dynamic characteristics of a cylindrical shell fixed vertically on a horizontal base by experiments and numerical analysis. Numerical code for the analysis has been developed by use of FEM and BEM.High speed ships have recently developed in Japan for the purpose of traffic modal shift. The local structures are in contact with rapid flow of water and can be damaged by flow induced vibration or unstable vibration. In the present study dynamic instability of a flat plate in contact with water has been studied. We make clear the critical velocity of relative speed by use of developed numerical code.