DISC FRICTION 



179 



been plotted from the experimental results for a pa-inted iron surface for 

 lengths up to 50 feet, and the curve thus obtained has been produced to 

 jive approximate values for lengths up to 330 feet. 



The results may thus be extended for application to the determination 

 of the frictional resistance of vessels of great length. For ships, the 

 value of n may be taken as 1*83, and the following table indicates results 

 obtained by exterpolation from the above curve : 



The following values of / are given by J. Hamilton 1 : 



AKT. 62. Disc FEICTION. 



The resistance to the rotation of a disc in water at high speeds is of 

 importance in the design of centrifugal pumps and turbines, the energy 

 expended in overcoming such resistances amounting in the case of some 

 high-speed pumps to as much as 15 per cent, of the total energy given 

 to the shaft. 



Theory of Disc Resistance. 



Assuming the resistance of an elementary ring of mean radius r and of 

 radial width Br to be given by / . 2 TT r Sr . v n , where / is a coefficient of 



. i Inst. Naval Architects,'' March, 1898. 



N 2 



