Investigating the Performance of Twin Marine Propellers in Different Ship Wake Fields Using an Unsteady Viscous and Inviscid Solver

Abstract

In this study, the performance of a twin-screw propeller under the influence of the wake field of a fully appended ship was investigated using a coupled Reynolds-averaged Navier—Stokes (RANS)/boundary element method (BEM) code. The unsteady BEM is an efficient approach to predicting propeller performance. By applying the time-stepping method in the BEM solver, the trailing vortex sheet pattern of the propeller can be accurately captured at each time step. This is the main innovation of the coupled strategy. Furthermore, to ascertain the effect of the wake field of the ship with acceptable accuracy, a RANS solver was developed. A finite volume method was used to discretize the Navier—Stokes equations on fully unstructured grids. To simulate ship motions, the volume of the fluid method was applied to the RANS solver. The validation of each solver (BEM/RANS) was separately performed, and the results were compared with experimental data. Ultimately, the BEM and RANS solvers were coupled to estimate the performance of a twin-screw propeller, which was affected by the wake field of the fully appended hull. The proposed model was applied to a twin-screw oceanography research vessel. The results demonstrated that the presented model can estimate the thrust coefficient of a propeller with good accuracy as compared to an experimental self-propulsion test. The wake sheet pattern of the propeller in open water (uniform flow) was also compared with the propeller in a real wake field.

Keywords

Twin propeller / Reynolds-averaged Navier—Stokes (RANS) / Boundary element method (BEM) / Time-stepping method (TSM) / Wake sheet pattern / Effective wake field