Research Of The Resistance And The Longitude Motion Of TRISWACH With Fins

High-performance ships, which accord with the new trend of the development of modern naval construction technology, will advance the productivity of human and reduce the cost of merchant shipping, and attract more and more attentions because of their advantages. Trimaran, one concept of high-performance ships, has been developing a lot. The advantages of its performance, which are acknowledged by researchers, have been proved by a great deal of researches and tests. Many kinds of different trimaran concepts have been presented in recent years. As a kind of trimaran, the concept of TRISWACH (trimaran with small waterplane area center hull) has its own characteristic and will have a wonderful future.TRISWACH has brilliant resistance and seakeeping performance, but because of the small waterplane area of the center hull it is easy to lose its longitudinal stability when sailing in high speed. So a couple of fins at bow are needed. And the flow field around TRISWACH becomes more complicated due to the existence of the fins. Meanwhile, the hydrodynamics of the TRISWACH has been changed considerably. It is very important to investigate the effects on the performance of a TRISWACH with fins.First the viscous flow field around the TRISWACH has been simulated with the CFD software FLUENT, in order to get the resistance and the configuration of the free surface. Meanwhile, the results of the calculation of the TRISWACH with different center hull have been compared. After then the flow field around the TRISWACH with fins has been simulated. Eighteen configurations of TRISWACH with fins, which were based on the size, the fixing positions and the attack angles of the fins, were chosen to analyze how these three factors above-mentioned affected the surface press on the fins, the resistance, the lift force, and the longitudinal moment. Finally, longitudinal motion of the TRISWACH had been calculated by the equations of motion which were modified by analyzing the force on the center hull and the fins.According to the paper if the ratio of the main axis to the minor axis of the transverse plane of the main hull was increased, the resistance of the ship would be increased, but the amplitude of the longitudinal motion would be reduced. The resistance of the TRISWACH with fins was bigger than the resistance of the naked ship, but the amplitude of the longitudinal motion was smaller than the naked ship's. Meanwhile, the resistance, the lift force and the longitudinal moment of the TRISWACH with fins would be increased when the size or the attack angle of the fins was increased, and increasing the horizontal projected area of the fins or setting the fins closer to the stem would take the better results of reducing the amplitude of the longitudinal motion of the ship.