70 



THEORETICAL AND EXPERIMENTAL STUDY 



ON THE DYNAMICS OF HYDROFOILS AS 



APPLIED TO NAVAL PROPELLERS 



E. Castagneto , ,. 



Istituto Architettura Navale . ^ 



Naples, Italy ;.<.::,. h 



., , , . . ., and \. .. ; . ^,,.., ,, , „■,. •..., .,, , ,,,■ 



P. G. Maioli 



Centra Esperienze Idrodinamiche i - 



Rome, Italy 



ABSTRACT 



The transformation of a hydrodynamic field into an actual propulsive 

 device follows a method which, although being derived from theory, is 

 based upon simplifications and approximations. Up till now no univocal 

 procedure has been proved by experience. 



The main reasons for this unsatisfactory situation seem to be: (a) dif- 

 ferences between hydrofoils' theoretical and actual perfornnances ; 

 (b) the effect of flow curvature in wide-bladed propellers. 



Since the hydrofoil's performance is one of the basic elements for the 

 majority of naval propulsive systems, conventional or not, it is intended 

 in this report to present some theoretical analyses and experimental 

 results dealing with thedynannics of hydrofoils. At the same time some 

 practical consequences of the effect of flow curvature are pointed out. 



1. INTRODUCTION 



In the design of a naval propeller based onthe vortex theory two main phases 

 may be considered: the evaluation of the hydrodynamic field for a limited num- 

 ber of radial stations, that is, the computation of both the velocity diagrams and 

 the products, lift coefficient x chord length {C^^- c) ; and the shaping of the re- 

 lated cylindrical blade sections in such a manner as to be able to produce the 

 desired lift without cavitation. 



The first phase follows a theoretical formulation, by now universally 

 adopted, which does not require any further comment; on the contrary, the sec- 

 ond one, in which the hydrodynamic field turns into an actual propulsive device, 



This work has been supported by the "Consiglio Nazionale delle Ricerche." 

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