Numerical Investigation of Significance of Duct Angle of Attack and Duct Position in a Ducted Propeller in the Presence of Propeller Boss Cap Fin

Currently propeller boss cap fin (PBCF) and propeller duct are among the well-known energy saving devices (ESD) for their effectiveness in recovery of energy losses during practical operation. These two devises prominently reduce the hub vortex as well tip vortex and hence improve propeller efficiency. Combined study of PBCF and propeller duct has become important and is essential to observe their impact in propeller efficiency. Here, numerically the importance of duct angle of attack and duct position in a ducted propeller in the presence of PBCF has been investigated to improve the overall efficiency. Five different angles of attack (0°, 2.5°, 5°, 7.5°, 10°) with 2.5° interval and five different positions (0.1, 0.15 m before propeller, at the propeller, 0.1, 0.15 m after the propeller) of duct have been considered to investigate the overall efficiency in the presence of both ESDs. Reynolds Average Navier Stokes (RANS) equations are utilized for numerical simulation in moving reference frame (MRF) approach. The simulations reveal that a maximum improvement of 7.05% is obtained in propeller efficiency at 0° angle of attack and it proportionally reduces with the increase in angle of attack. It is also observed that duct placed before propeller produced a maximum enhancement in efficiency of about 9.86% in comparison with other duct positions. Variation of pressure coefficient, vortices, skin friction coefficient and turbulence kinetic energy are also studied in detail in order to have a better understanding about the flow behaviour.