Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGFigure 25-2. -Hydrofoil in flight.3.88The super cavitating (SC) propeller is a recentdevelopment that may have particular applicationto hydrofoils and other high speed ships. Thesupercavitating propeller is intended for use athigh forward speeds and high rpm, with a relativelyshallow depth of submergence. It is designedto operate under conditions of full cavitation,although it may encounter conditions ofpartial cavitation when operating at less thandesigned forward speed and rpm. Under conditionsof partial cavitation, the supercavitatingpropeller may be subject to cavitation erosionsimilar to that encountered on conventional propellers.A supercavitating propeller is designed tooperate with the suction side (back) of the bladesenclosed in avapor cavity. Because of the specialdesign of the blades, this vapor cavity collapsesfar enough downstream from the propeller bladesto prevent any cavitation effects on the face of theblades. In essence, the basic line of reasoning behindthe design of the supercavitating propelleris not to do away with or prevent cavitation butrather to accept it as inevitable at high speedsand to control it. The supercavitating propellercontrols cavitation by making sure that the cavitycollapse occurs in an area in which it can do relativelylittle damage.632