Design of Energy-Saving Duct for JBC to Reduce Ship Resistance by CFD Method

The present work is to modify the stern duct of Japan bulk carrier (JBC) to reduce the ship total resistance for Froude number 0.142. The research method is to use the CFD (computational fluid dynamics) tool OpenFOAM to predict the total resistance and viscous flow field around the ship hull considering the free surface. First, the V&V (verification and validation) analysis was conducted to ensure our CFD method is reliable, and to estimate its error and uncertainty range for the original JBC with and without the original stern duct. Second, the angle of attack (AoA) of the foil section of the stern duct was adjusted, thus forming a series of different ducts axisymmetric along the propeller shaft axis. The CFD simulations were performed for each duct appended behind the ship hull. By comparing the total resistance with and without the duct, the ship hull resistance reduction effect caused by the duct would be obtained. Finally, the duct with 7 (Formula presented.) AoA achieved the best resistance reduction of 2.49%. The original duct (with 20 (Formula presented.) AoA) could only provide a 0.6~0.7% reduction. The nominal wake was also analyzed with the ducts, in order to understand the detailed flow phenomena which had an essential influence on propeller inflow.