追波中を航行する船体に働く流体力について(第1報)

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Broaching phenomena are most likely to occur in a following sea to relative small and fast craft under the condition that the wavelength/the ship length ratio is about 1.5 to 2.O. There are many studies and explanations about it, and it is thought that the forces acting on the ship are almost consist of the hydrostatic force and steady state lift. Towing flat plate model in following waves without attack angle it become obvious that side force and heading moment are of such magnitude as to a marked extend. These changed or additional disturbing forces depend upon the wave height and upon the relative position of the ship to waves. In this paper two attempt are made in order to investigate the hydrodynamic force. Firstly, transforming vortex core model is used under the assumption of the free surface is flat. Slender-rectangular thin wing in the constant stream, 3-dimensional separation occurs at the end of the side edges, which form a symmetrical spiral vortex sheet. In a following sea, these spiral vortex sheet may be affected by the wave orbital velocity. A simple flow model, consists of core vortices and feed vortex sheets which emerge from side edges to the core vortices, is used. And core vortices are transformed by the wave orbital velocity and the induced velocities of vortices. By the method, reasonable results are obtained for normal force coefficient, centre of pressure and location of the core vortex in the constant flow. But in a following sea, calculated normal force coefficient is not so good. Secondly, high speed slender body theory is used introducing the data of incident wave as free surface. These method, calculated normal force and heading moment coefficients show quite good agreement to the data obtained from towing flat plate model test.
社団法人日本船舶海洋工学会の論文

追波中を航行する船体に働く流体力について(第1報)

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