Lift Mechanism Of Ship Morphing Anti-rolling Fin And Model Research

The principal of fin stabilizers is to utilize the lift produced at the stabilizers to fight back the rolling torque.Therefore,the stabilization effect would be better should the lift increased.A fin stabilizer designed by variant designing could realize lift increasing only by changing the shape of wall surface,and the stabilization performance would be improved by combining some control algorithms.The model establishment for variant fin stabilizer's lift is very important for future fin stabilizer design.There exist a number of modeling methods;however,these methods could not be applied to fin stabilizers due to its uniqueness.In this thesis,CFD software is used in the modeling of the variant fin stabilizers.The lift coefficients are optimized by introducing the thought in which fluid flowing on the surface of fin stabilizers is controlled.By varying shapes of the fin stabilizer,the fluid could flow in a wanted direction so that the lift could be enhanced without changing attack angel.The modeling process is a CFD computing process in fact.A lift increasing scheme by varying leading edge of the fin stabilizer is presented according to the boundary-layer theorem which is deducted form the hydrodynamics Newton momentum theorem.Initial computation demonstrates that the shape variance of leading edge could increase the lift to a large degree.In the last chapter,a fin stabilizer imitating humpback whale's front fin is proposed with the help of bionics.Scientific researches show that tubercles part at the humpback whale's front fin could help enhance the lift.In this thesis,a new fin stabilizer is presented based on the humpback whale's front fin which has a sine-shape tubercle at the leading edge.With the help of FLUENT software, numerical simulation of the flow field has been conducted on this new fin stabilizer.Compared with experimental data generated by NACA0015 fin stabilizer with the same geometric standard,the new fin stabilizers established in this thesis could yield more lift.Sensitivity and effectiveness of the new fin stabilizer's parameters are calculated to select a model which could provide the largest lift on the basis of which simulation work of stabilizing under ocean wave conditions is done.