Hydrodynamic Problems Solved by Rheoelectric Analogies 



is unable to provide. Only the theory of the lifting surface, applied to the marine 

 propeller, is able to solve these two problems. 



Theory of the Lifting Surface of the Screw Propeller— The linearized lifting 

 surface theory, often used in the case of wings, can easily be adopted for the 

 screw propeller. 



Assume that the propeller's blades are infinitely thin, inducing only a small 

 perturbation in the relative flow resulting from the uniform velocity Vq in the 

 negative direction of the z-axis and the angular velocity ^ around this axis, and 

 that the blades lie on a helicoidal flow- surface of the nondisturbed flow (Fig. 22). 

 For a p-bladed propeller with maximum radius R, the perturbation velocity 

 field is periodical in space and the study is thus confined to a region between two 

 helicoidal surfaces deduced from one another by a rotation of a 27t/P angle. The 

 flow field is defined by the following boundary conditions of the perturbation ve- 

 locities potential 4>' . 



Fig. 2Z - Screw propeller blades 

 on a helicoidal flow -surface of 

 nondisturbed flow 



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