Numerical simulation of wake field and propulsion performance in a four-screw ship

Abstract

Computational studies using the Reynolds Averaged Navier–Stokes (RANS) method on viscous wake fields and the propulsion performance of a four-screw ship were conducted. The self-propulsion experimental investigation was carried out in a towing tank to analyze the propulsion performance of the four-screw ship. The characteristics of the wake field and hydrodynamic performance of the inside and outside propellers were compared in detail. The computational fluid dynamics results and experimental data showed good agreement. There were considerably different distribution patterns of the wake field between inside and outside the propeller disc, especially in the zone behind the brackets. The mean axial velocity at different radii of the inside propeller is generally smaller than that of the outside propeller, which results in the time-averaged loads of the inside propeller becoming larger than those of the outside one. Harmonics analysis indicates that in the considered range of the outer radii, the 1st and 2nd order harmonic components of the inside propeller disc are larger than those of the outside one, which causes the fluctuation amplitudes of the loads on the inside propeller to become higher than those of the outside one.