Numerical investigation on the effect of shaft inclination angle on hydrodynamic characteristics of a surface-piercing propeller

The global demand for fast sea transportation has led to an ongoing development of high-speed vessels and surface-piercing propeller, as a high performance propulsor, has played an important role in this development. However, the complexity of the two-phase flow field around the propeller has made its numerical analysis enough challenging. The performance of surface-piercing propeller depends on propeller geometric parameters and flow conditions at propeller disk. Among these parameters, shaft inclination angle is a key parameter which significantly affects the flow conditions at propeller disk. In this paper, RANS computations were applied to investigate the unsteady flow around an optimized surface-pricing propeller in various shaft inclination angles. Likewise, the homogeneous Eulerian multiphase model was employed along with Volume of Fluid model to solve the two-phase flow field equations. Rotational motion of the propeller was simulated by CFX sliding mesh technique. The effect of shaft inclination angle on the hydrodynamic coefficients of the propeller and the behavior of the fluid flow around the propeller key blade are among the principal objectives clarified in this study. As the results indicated, the propeller thrust and torque coefficients were gone up with an increase in the shaft inclination angle. Moreover, as the shaft inclination angle increases, the maximum thrust and torque coefficients of the key blade take place at the lower rotation angles. Additionally, it was revealed that the effect of shaft inclination angle on the torque coefficient of the key blade depends on the angular position of the key blade. Furthermore, the flow patterns around the propeller were predicted in different shaft inclination angles. In order to verify the accuracy of the numerical method used in this paper, numerical simulations were run on SPP-841B propeller with available experimental data. The comparison between the simulated and measured SPP-841B open characteristics as well as the ventilation pattern of the key blade indicates a reasonable agreement with the experimental data.