Study on the relation between propulsion factors and velocity field of flow in the propeller disk behind the hull 1

Abstract

The author has studied the relationship between the propulsion factors, which are effective wake factor, thrust deduction factor and relative rotative efficiency, and other elements of ship performance, and the non-uniform velocity field of flow in the propeller disk behind the hull. This is based on a calculation method employing a mathematical model of the hydrodynamical action of a propeller. This study has made it possible to understand the physical meanings of the effective wake and the relative rotative efficiency, and to consider the scale effects on all propulsion factors in a practical way. Subsequently the effects of the non-uniformity of flow on the propulsion factors have been made clear. When the wake pattern of the full scale ship is estimated by the Sasajima-Tanaka method or other estimation method, the thrust, torque and power generated by the actual propeller behind the full scale ship can be predicted. The predicted results of a numerical example for a large oil tanker have shown a good agreement with the trial results.