Numerical investigation on the flow characteristics and hydrodynamic performance of tandem propeller

Abstract

The hydrodynamic performance of tandem propeller (two co-rotating KP458 propellers) is investigated by an FVM (Finite Volume Method) based approach in this study. The effects of advance ratio J (0 ≤ J ≤ 0.7), spacing ratio (0.26 ≤ L/Df ≤ 0.34) and diameter ratio (0.92 ≤ Da/Df ≤ 0.97) are comprehensively studied and analyzed. A three-dimensional cubic computational domain is considered in this study, and the MRF (Moving Reference Frame) approach is adopted to handle the rotation of the tandem propeller mathematically. Turbulence is accounted for with the RNG k-ε model. It is demonstrated that the hydrodynamic forces maximize at a spacing ratio of 0.29 if the diameter ratio equals 1.0. It is also found that the efficiency is improved by approximately 45% for the tandem propeller with the diameter ratio being 0.95 at L/Df = 0.29, compared to the single propeller, at J = 0.7. In addition, by appropriately specifying the spacing ratio or the diameter ratio, the rotation of rear propeller could well absorb the energy of the trailing vortices shed from the front propeller. Consequently, the trailing vortices are rapidly dissipated and disappear in the wake field after merging, and a better hydrodynamic performance can be obtained.