Interference Effects Between the Hull, Propeller and Rudder of a Hydrodynamic Mathematical Model in Maneuvering Motion

Abstract

Many expressions of hydrodynamic forces on a ship are proposed to construct a mathematical model for describing maneuvering motion. One of them is the mathematical model which expresses hydrodynamic forces by considering the individual open-water characteristics of the hull, propeller and rudder and the interference effects among them. This mathematical model began to be commonly used because of its convenience in practical usage and rationality. However, when applying the model to a full shape ship and predicting maneuvering motion at large helm angles by the analized results of the ordinary captive model tests, the predicted motions were very different from the measured motions of the free running tests. And it was found that the difference was caused by the poor treatment of interference effects between the hull, propeller and rudder. In this paper, we proposed to settle the problem by carrying out circular motion tests which correspond to steady turning. Further, we analized the test results and derived new expressions for the interference effects. The present coefficients describing interference effects were arranged together with the ship particulars, so they can be easily treated in the program for numerical simulations. Lastly, the prediction of maneuvering motions corresponding to the free running tests were made. Judging from the good coincidence between the predicted results and the measured ones, the new mathematical model was proved appropriate for describing interference effects.