Response of Slowly Moving Ship to Propeller and Rudder Actions

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Response of Slowly Moving Ship to Propeller and Rudder Actions

C. L. Crane

An attempt is made to extend ship maneuvering analysis for application at low ship speeds. Experiments are made with captive-model to investigate effects of non-equilibrium propeller speeds on rudder force and effective thrust. Other experiments are made to explore first-order effects of very large drift angles and pure yaw rotation on hull hydrodynamic reactions. The experimental results, together with previous rotating-arm data, are applied in motion equations, accounting for both extreme propeller actions and the occurrence of large drift angles and turning rates. Also included are propulsion and rudder time lags, and the influence of uniform water-current on ship trajectory. The equations are programmed for computation, and ship response to a simple docking maneuver is predicted. The computation is repeated several times to examine sensitivity of ship motions and trajectory to variations of operating parameters; namely, maximum reverse propeller-speed, engine response time, and water-current direction. (Author)