EFFECTS OF SHIP HULL AND PROPELLER ON RUDDER CAVITATION

Ship trial observation and drydock inspection of a surface ship combat ant show that rudder cavitation can be a real problem in terms of ship operation and maintenance. A project has been initiated by the Navy ( a) to identify fleet rudder cavitation problem, (b) to investigate exp erimentally and numerically hull/propeller effects on rudder cavitatio n, and (c) to develop methods to incorporate propeller/rudder interact ion into the future rudder design for cavitation improvement. Experime nts 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 surfac e combatant. Two-component Laser Doppler Velocimetry (LDV) was used to measure the field velocity and inflow angles in the propeller slipstr eam. A dynamometer and pressure taps were used to measure rudder lift, drag and pressure distributions. Influence of the ship hull and prope ller on rudder forces, pressure distribution, and cavitation performan ce are compared with numerical calculations. The resemblance between t he model rudder cavitation pattern in the LCC and full-scale cavitatio n erosion pattern observed in the dry dock is discussed.