Study on New Air-ship Form Bulb for High Speed Displacement Type Hull Form

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In recent years, many ideas are proposed in order to pursue the high speed vessel. Many of those ideas are based on unconventional concepts such as the application of hydrodynamic lift generated by wings. In those cases, however, we have many problems for the purpose of sizing up and long distance voyage. As well known, conventional ship, that is a displacement type, has more merits than unconventional ones at least from point of view of buoyancy. Therefore it can be considered as one of the effective ways to pursue the high speed vessel based on the concept of displacement type.In the present study, minimization of wave resistance of a special type ship in high speed range is discussed according to the concept of wave making interference between a main hull and an air-ship form bulb. This bulb is formed by the combination of a hydrodynamic point source and a line sink, semi-splitted from the main hull of displacement type and supported by the strut. Wave resistance of this special type ship is minimized under some design conditions by means of nonlinear programming. Experimental investigations are carried out for two selected models which have the air-ship form bulb and the main hull of the mathematical water lines and frame lines optimized by the present theory. After showing the model test results of fixed trim conditions and free trim conditions, some discussions about the direction of model improvements are given. In order to adopt the air-ship form bulb as the practical bulbous bow, the effect of an entrance angle of the main hull, the control of the trim and so on are investigated experimentally.