Hydrodynamic Characteristic Analysis Of Deformation Fin And Control Strategy Research At Low Speed

As a high or medium speed roll stabilizer device, fin stabilizer always catches people’seyes, because the roll reduction could reach90%. However, the traditional fins have ashortcoming, that when the flow of the water past fin has a low speed, the fin stabilizer almosthas no effect, in connection with mechanism of reducing force of fin stabilizer. But shipsalways spend so much time anchoring at harbor, or because of some special tasks, neednavigating at low speed, now we has a very hard problem to solve. Always the resolution is toinstall anti-roll tanks or bilge heels when ship has fin stabilizer already, it means there are twokinds of stabilizer device to design and maintain, and it needs more people, more materialsand more cost, and without question it’s a big pressure. Meanwhile, because anti-roll tank isthe main roll stabilizer device at zero or low speed, but only when the oscillation naturalfrequency of water in tank is close the ship’s roll frequency, it could reach a good rollreduction, if they are too different, the anti-roll tank could enhance the roll.Because of they working poorly at low speed and not at all when adrift or anchored, thisarticle put forward a new fin called Deformation fin, from appearance it has small span-chordratio, the axis of the fin is more nearer to forward edge, and there is a small fin inside themain fin that is retractable. For the function of the deformation fin, the main purpose of usingthis kind of fin is to achieve effective of all speed of ship, with different speed, the installmethod is same, but the way it flaps is different. The similar idea is come out home andabroad very early, and many researchers already have done many deep researches, but theyput emphasis on stabilizing at zero speed. But the strategy of fin stabilizers when ship is atlow speed is not deep researched.The main content of this article is, first we analysis the way of the fin move and themechanism of the fin producing lift when the ship at high-medium speed or at low-zero speed;then analysis which factors can effect the fin’s hydrodynamic characteristic and how; becausethe main problem of the fin at low speed is that it can not produce enough lift to reduce theroll of the ship, so the article go further discuss how to find a optimal movement, that couldproduce the larger lift to reduce ship roll better. Because of the most researches before putemphasis on high-medium or low speed, so the article will relatively complete to discuss thestrategy problems of the fin at low speed.The last part of this article will give the simulation method and result of the long randomwave, it will be a wave disturbance input as a module of the Deformation fin system that will be build at MATLAB/simulink. With setting up different parameters, to analysis the rollreduction and system performance of the fin at different sea conditions.