Research On Fin Hydrodynamic Applications And Combined Fin/Tanks Anti-Roll System

In order to well reduce ship rolling in different ship sailing conditions(mid -high speed, low speed and zero speed; different encounter directions), the best way is to use the integrant fin stabilizer and anti-roll tank control system, and to get the two devices coordinate combination and reasonably configuration, so as to reduce the ship rolling into full play.It is the purpose to reduce ship rolling in different ship sailing conditions by using the fin stabilizer and anti-roll tank as the basic control units; in modeling, simulation and optimization the individual parts of the combination anti-roll devices, put the stress on the research design works to get reasonably combination anti-roll devices configuration and well roll reducing . The research works in the dissertation are as following:Based on analysis on statistic and dynamic hydro-dynamic forces data of the fin models in towing tank in different conditions, put forward a multinomial fitting method using least square method to deal with the measured errors of the hydro-dynamic forces data. The method is powerful to treat rough data. The draft hydro-dynamic force coefficients are fitted by using segment multinomial, and the lift forces and torque ones are fitted by combined with segment multinomial and conic sections.In order to put dynamic hydro-dynamic forces to fins, based on dynamic hydro-dynamic force curves of fin models, a BP neural network is applied to fitting dynamic hydro-dynamic force curves, and a lift signal generator is put up. By using this way, the hydro-dynamic forces caused by a random sea are applied to simulate the lift of a random moved fin. The way was used to the platform test of a lift controlled fin stabilizer.Using the coupled coefficients of forward to stern fins, the disturbance of stern fin lift by forward fin is analyzed. The lift decrease is compensated by a controller of fin stabilizer. As a result, the total roll reducing effectiveness of twofins is increased.In fm stabilizer design, dynamic hydro-dynamic force coefficient is used to replace statistic hydro-dynamic force to calculated fin lift. In order to determine the well driven fin power of a servo, a dynamic hydro-dynamic torque coefficient is used to replace statistic one .A parameters frequency response method is applied to simulate ship roll response equipped two anti-roll tanks with different nature frequencies. It can be seen that four parameters of tank nature frequency, non-dimension decay coefficient, parameter k2 with low nature frequency tank and vertical arrangement of tank, which denote anti-roll tank characteristics, affect the roll response of tank.The dynamic model of a RO/RO ship equipped a combined anti-roll device with a fin stabilizer and two anti-roll tanks is studied. The control system model of the combined anti-roll device is set up. The combined anti-roll device of a fin stabilizer and double anti-roll tanks is given. Final a combined anti-roll device of a low capacity fin stabilizer and a double anti-roll tank with smaller dimension is studied in the dissertation.The studies in the dissertation are based on the towing tank hydro-dynamic data and fin stabilizer design methods of Harbin Engineering University. The research results can be referred in the study and design of fin stabilizers, anti-roll tank, and combined anti-roll device.