Computations of Propeller Performances Under the Influences of Free Surface and Ship Motions

• Main Authors: Lai, Sin-An, 賴信安
• Other Authors: Hsin, Ching-Yeh
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/t26y3h

碩士 === 國立臺灣海洋大學 === 系統工程暨造船學系 === 106 === In this thesis, the propeller performance in seaway is investigated by computations. In order to understand different effects individually, three different situations, incline shaft, ship motion and free surface are discussed. We can categorize incline shaft and ship motion effects as inflow variations due to ship position changes, and free surface effect as change of the physical environment around the propeller. Steady and unsteady viscous flow RANS methods, steady and unsteady potential flow boundary element method are used as computational methods for analysis. A container ship propeller H1 and a Kappel propeller designed based on H1 propeller performance, H1K are used for computations. Since propeller in inclined shaft computations are the fundamental simulations of propeller in ship motions, the angles of the inclined shaft are first varied from 0 to 30 degrees to understand the influence of non-uniform flow to the propeller performance. The influences of heave and pitch motions to the propeller performance are then investigated. Both quasi-steady simulation and unsteady simulation are adopted to understand the thrust and torque variations during ship motions. It is found that the quasi-steady simulation can get accurate mean forces in shorter computational time; however, only unsteady simulation can obtain correct phase and time history of forces. Finally, the free surface effects are studied. By ignoring cavitation and ventilation, propellers forces and flow field close to free surface are computed and analyzed to understand the interactions between free surface and propellers. Results of propellers under the influence of free surface and ship motions in this thesis can be used for researching more complex problems in the future.