In this paper, scale effect of PBCF at different advance coefficients is investigated using IDDES turbulence model and sliding mesh technique. Predicted results of thrust and torque coefficients at different advance coefficients agree well with their experimental counterparts. Numerical results indicate that PBCF can obtain a net propulsion efficiency improvement of 2% in the model scale. The augmentation of the propeller efficiency by full scale model is significantly twice as much as that of the model scale.
In recent years, the International Maritime Organization (IMO) has speeded up the implementation of green shipbuilding and the limitation of greenhouse gas emissions from newly built ships. EEDI (Energy Efficiency Design Index) representing the energy efficiency of the ship is set up to establish a minimum energy efficiency standard for ships in the future. As a result, huge attention is drawn to the research of improving the propulsion efficiency of propeller.
PBCF (Propeller Boss Cap Fins) is a kind of energy-saving devices which is installed behind the propeller and rotates along with the propeller as shown in the Fig. 1. Since the introduction in 1987, it is used widely for its good performance. Kurt et al. (2017) used the CFD commercial software STAR-CCM+ to do the design and the optimization of the PBCF. Series of parameters which had effect on the energy-saving of the PBCF were focused on. The general stage of the design and the optimization were summarized. The best achievement in improving efficiency by adding PBCF was about 1.3%. Chao Wang et al. (2009) analyzed thrust coefficient, torque coefficient, pressure distribution of propeller blade surface and velocity distribution of hub surface of PBCF at different advanced coefficients. Through showing details of flow field using CFD, it found that fin could effectively change the flow velocity distribution at the hub, making the flow of water which originally revolved around the propeller move along the fin to the rear of the propeller. Druckenbrod et al. (2015) studied the optimization process of the CFD method for the design of PBCF. The optimization process was divided into two steps: the first step was to consider the change of propeller thrust, torque and efficiency after installing the hub and cap fin while the second step started with the hub vortex of the propeller and tried to minimize the hub vortex strength as far as possible. Berger et al. (2013) focused on the optimization design process of the hub fins with the method of CFD. Dang et al. (2012) investigated the detailed flow field of the propulsion system with the PSS using PIV and CFD two methods. It drew the conclusion that the CFD method had the ability to catch the detail and possible separation of the flow. The calculation result from the CFD method was in good agreement with that from the measurement of the PIV It indicated the reliable ofthe CFD method. Yan Ma et al. (2011) used the RANS solver of CFD commercial software FLUENT to do the performance calculation of a 57000DWT bulk carrier. In the calculation, the SST k-ω turbulence model was used and the decoupling of velocity and pressure was based on the SIMPLE algorithm. The discrete equations were solved by Gauss-Seidel method and the algebraic multigrid was adopted to accelerate the solving speed. Propellers with and without PBCF were simulated to study energy saving effect of PBCF.
