ANALYTICAL PREDICTION OF THRUST DEDUCTION FOR SUBMERSIBLES AND SURFACE SHIPS

An analytical method which is based on the Lagally steady-motion theorem is presented for the numerical calculation of thrust deduction for body and propeller systems. It is assumed that the influence of a propeller on a hull is mainly potential in origin, whereas the influence of the hull on the propeller is essentially viscous in origin. In the method, a lifting-line representation is used for the propeller, the potential flow due to the hull is obtained from the Douglas-Neumann program, and the real total wake is determined experimentally. Thrust deduction computations for a bare hull and an appended body of revolution, and a low-speed single-screw surface ship are in good agreement with the thrust deduction derived from propulsion tests of these vehicles. The results of a limited study of the effect on thrust deduction of propeller position and propeller radial thrust distribution are given.