Experiment on the Frictional Resistance of Rotating Disc

Abstract

In this paper, the results of the experiment on the frictional resistance of rotating disc in a casing are described. The theoretical calculation of this problem, is already carried out by B. Hudimoto and the author. Denoting M=ρω2r05Cf/2, R=r0ω2/ν, where M is the moment of the frictional resistance, ω is the angular velocity of the rotating disc, r0 is the radius of the disc, ρ and ν are density and kinematic viscosity of fluid in a casing respectively, ω is the coefficient of the moment and R is Reynolds number, the results of the experiment are shown by the relation between Cf and R. The experiments are carried out for the next four cases, using the air as the fluid in a casing, and Reynolds number R is varied from 5×104 to 4×105. (1) smooth disc and smooth casing. (2) rough disc and smooth casing. (3) smooth disc and rough casing. (4) rough disc and rough casing. The rough surface is made up by passing the sand on the surface and the roughness is shown by the parameter r0/k, k being the mean diameter of the sand. Moreover, in the case (1), the axial distance 8 between the disc and the casing is varied and this influence is shown by the parameter r0/s.