PRINCIPLES OF NAVAL ENGINEERING 



3.88 



Figure 25-2. -Hydrofoil in flight. 



The super cavitating (SC) propeller is a recent 

 development that may have particular application 

 to hydrofoils and other high speed ships. The 

 supercavitating propeller is intended for use at 

 high forward speeds and high rpm, with a re- 

 latively shallow depth of submergence. It is de- 

 signed to operate under conditions of full cavi- 

 tation, although it may encounter conditions of 

 partial cavitation when operating at less than 

 designed forward speed and rpm. Under condi- 

 tions of partial cavitation, the supercavitating 

 propeller may be subject to cavitation erosion 

 similar to that encountered on conventional pro- 

 pellers. 



A supercavitating propeller is designed to 

 operate with the suction side (back) of the blades 

 enclosed in avapor cavity. Because of the special 

 design of the blades, this vapor cavity collapses 

 far enough downstream from the propeller blades 

 to prevent any cavitation effects on the face of the 

 blades. In essence, the basic line of reasoning be- 

 hind the design of the supercavitating propeller 

 is not to do away with or prevent cavitation but 

 rather to accept it as inevitable at high speeds 

 and to control it. The supercavitating propeller 

 controls cavitation by making sure that the cavity 

 collapse occurs in an area in which it can do re- 

 latively little damage. 



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