Titoff, Russetsky, and Georgiyevskaya 



Vo. +WS -Wk 



"" ^^F^. 



Fig. 2 - Cavitating propeller performance 



characterizing the streamline shape in the way of the blades will be defined as 

 the sum total of the velocities w^g and WtB induced by the vortices and the ve- 

 locity Wgj^ which is due to the thickness effect of cavities (Fig. 3). Since the 

 velocity w^j^ increases from the leading edge in the direction of flow, an addi- 

 tional bending of the streamline takes place. On the basis of the assumptions 

 made above, the calculation of the streamline shape enables us to obtain initial 

 data for the deflection of the blade element section. 



Fig. 3 - Local velocity of a blade streamline 



The above method can be applied, if we know the thickness and the increase 

 of thickness law for cavities developing on the blades. 



It has been shown by analysis and checking the calculation that using data on 

 the thicknesses of cavities for separate sections does not yield satisfactory re- 

 sults, and this apparently is attributable to the effect of the blades. That is why 

 theoretical calculation was subsequently made only for the law of cavity increase, 

 while the value of thickness was taken from the results of measurements con- 

 ducted on propeller models. 



Systematic measurements carried out by E.A. Fisher have made it possible 

 to obtain the thickness of a cavity on the trailing edge versus the nominal angle 

 of attack at infinity for various geometrical elements of the blade (e.g., curva- 

 ture, shape of blade section, etc.). A diagram of such a measurement is given 

 in Fig. 4. When using experimental diagrams, the use of the method of succes- 

 sive approximations is considered necessary; however, this does not involve 



d22 



