WATER-JET PROPULSION 

 FOR HIGH-SPEED SURFACE SHIPS 



Jacques Duport, Michel Visconti, Jean Merle 



SOGREAH 

 Grenoble j France 



ABSTRACT 



Free-stream subcavitating propellers are not proper 

 for very high-speed surface crafts. The range of 

 speed where subcavitating impellers can be used is 

 largely increased when the propulsion flow is sepa- 

 rated from the main external flow, i.e. when water- 

 jet propulsion systems are being used. 



A great variety of water-jet propellers can be pro- 

 posed depending mainly on the jet-velocity ratio 

 ( then on the rate of flow ) , and the arrangement 

 of water circuits (either fully or partially submerged, 

 either straight-flow or elbowed circuits, etc. ). 



A common method of approach, applying to any of 

 these, is proposed for the determination of the hy- 

 drodynamic characteristics of the propeller system. 

 This concerns principally : 



. Energy balance of both internal and external flows, 

 . Mutual interaction of both flows (including eventual 



hull interaction), 



Cavitation limits, 



Dimensionless hydrodynamic parameters. 



The hydrodynamics of internal flow can be to a large 

 extent analysed separately from the external flow 

 analysis. This is a source of considerable simplifi- 

 cation for both theoretical and experimental appro- 

 aches. 



