Effects of Ship Hull and Propeller on Rudder Cavitation

Abstract

Ship trial observation and drydock inspection of a surface ship combatant show that rudder cavitation can be a real problem in terms of ship operation and maintenance. A project has been initiated by the Navyto identify fleet rudder cavitation problem,to investigate experimentally and numerically hull/propeller effects on rudder cavitation, andto develop methods to incorporate propeller/rudder interaction into the future rudder design for cavitation improvement. Experiments were carried out at the Navy's Large Cavitation Channel (LCC) with a geosim model of a fleet rudder, propeller and ship hull of a surface combatant. Two-component Laser DopplerVelocimetry (LDV) was used to measure the field velocity and inflow angles in the propeller slipstream. A dynamometer and pressure taps were used to measure rudder lift, drag and pressure distributions. Influence of the ship hull and propeller on rudder forces, pressure distribution, and cavitation performance are compared with numerical calculations. The resemblance between the model rudder cavitation pattern in the LCC and full-scale cavitation erosion pattern observed in the dry dock is discussed.