Numerical Simulation For Hydrodynamic Analysis Of Roll Stabilizer Fins At Zero Speed

With the rapid development of ship and ocean engineering,most kind of ships are required to have a higher rolling stability. The most useful anti-roll equipment is almost the fin stabilizer because it can reduce the most roll of the ship under high speed. The high efficiency of conventional fin stabilizing system depends on a large current difference between fin stabilizer and the liquid, but it has the poor performance at zero or low speed, so roll fin stabilizer at zero speed has been getting increasingly great attention in recent years.In the thesis,the development status of the roll fin stabilizers at zero speed is introduced firstly, and the operational mode of the roll fin stabilizers at zero speed is described briefly.Then, the key technology to design roll fin stabilizer at zero speed, which is to analyze the hydrodynamic characteristics of roll fin stabilizer at zero speed correctly, is confirmed.Secondly, a 2D grid-free discrete vortex model is established. Not only flow past a fixed cylinder, but also flow past an oscillating cylinder has been simulated in present work. Then Discrete Vortex Method and Surface Panel Method is compared and analyzed for finding the merits and drawbacks when they are used to research the hydrodynamic characteristics of roll fin stabilizer at zero speed and Surface Panel Method is employed.Thirdly, the governing equation and boundary conditions are formulated, Surface Panel Method is invoked to solve the governing. According to the characteristics of the operational mode of the roll fin stabilizers at zero speed, mechanical parameters are established, which is effective to represent and judge the effect of anti-roll.Finally, Surface Panel Method is applied to simulate the impulsively started problem of a two-dimensional airfoil. Comparing calculated lift coefficient with Wagner function, there exists little difference. Other numerical results also have a good agreement with experimental data. Different position of the rotational axis, different frequency, different airfoil are computed for analyzing hydrodynamic characteristics of roll fin stabilizer. The relationship between the performance of anti-roll and the factors is also investigated in order to provide some valuable parameters in the preliminary design of the Roll Fin Stabilizers at zero speed.