Cox 



Basically, there are five separate phases to the design of any propeller, 

 namely: 



(a) preliminary powering analysis to determine the design parameters 

 for which the propeller is to be designed, i.e., thrust loading coefficient c^, 

 advance ratio k, number of blades Q, etc., such that the propeller is compati- 

 ble with the craft, installed propulsion machinery and transmission; 



(b) determination of the relationship between propeller performance 

 and design parameters in viscous and inviscid flow. This procedure is neces- 

 sary since, essentially, the basic design process is concerned with behavior in 

 inviscid flow; 



(c) determination of desired blade radial lift distribution together with 

 radial induced hydrodynamic pitch angle (hence thrust and torque distribution), 

 for operation in inviscid flow; 



(d) determination of blade shape and area; camber, pitch, and thick- 

 ness distribution to actually achieve the desired requirements of (c); 



(e) a strength check. 



For a subcavitating propeller it is necessary to augment (d) with the require- 

 ment for freedom from cavitation erosion and thrust breakdown at the design 

 condition. For a supercavitating propeller it is necessary to augment (a), (b), 

 and (d) by the following: 



for (a) ~ ensure that the design parameters are chosen to permit 



the blades to operate effectively in a supercavitating regime; 



for (b) ~ although blade cavity-pressure drag is an inviscid flow pa- 

 rameter, it is best to consider it in association with blade 

 viscous drag. Hence for design purposes inviscid flow per- 

 formance is defined to omit blade cavity-pressure drag; 



for (d) — ensure freedom from blade pressure- side (face) cavitation, 

 and that the blade thickness lies within the upper cavity 

 boundary. K necessary, due to blade thickness requirements 

 or circumferential wake variations, an operating angle of 

 attack is selected for the blade at the design condition. 



The importance of preliminary design analysis cannot be overstressed, but 

 will not be considered here, since it involves many aspects of naval architec- 

 ture not concerned with detailed propeller design theory. It is, of course, inti- 

 mately concerned with the theoretically predicted [7], or experimentally meas- 

 ured [8], performance for systematic series of propellers. Likewise, the subject 

 of propeller blade strength can be considered independently of a particular theo- 

 retical design procedure, although use is made of intermediate results deter- 

 mined in the basic design process. Hence, the main emphasis of theoretical 

 propeller design is usually considered to be concerned with phases (b), (c), and 

 (d). It is important to realize that phases (b) and (c) are concerned with 



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