The effects of pre-swirl ducts on the propulsion performance of conventional ship: an experimental study

In the current study, the propulsion performance of a conventional ship is experimentally evaluated via self-propulsion tests under four different pre-swirl ducts compared to a case with no duct. For this purpose, the Series-60 ship was used as an intended conventional ship and the Mewis duct, the semicircular duct, and the Becker twisted fins duct were investigated. We also tested an improved Mewis duct by changing its hydrofoil section and chord length. The thrust and torque coefficients and the propulsive efficiency were analyzed to investigate the propulsion performance. According to our experimental measurements, we found that the thrust coefficient was increased and the torque coefficient was decreased using pre-swirl ducts compared to the case with no duct, especially for a higher Froude number. The highest value for the propulsive efficiency was achieved for the Mewis duct, the Becker twisted fins duct, and the semicircular duct, in the order of their appearance. We also found that the reduction in the Mewis duct's chord length and a change in its hydrofoil type from the NACA4415 to the Nozzle A19 result in an increase in the propulsive efficiency.