Experimental Characterization of Flow Regimes for a Rotating Disc Over a Range of Gas Pressures

Abstract

Experimental measurement of viscous drag is done on a rotating disc using a disc spin-down experiment in various air pressures ranging from atmospheric pressure through a vacuum pressure of 0.3 kPa. The torque is non-dimensionalized using the dynamic viscosity of air, angular velocity, and the characteristic dimension of the disc. The results can be classified as two different sets. Between atmospheric pressure and 13.3 kPa, the curves have a vertical downward trend and are connected to each other while at lower pressures the curves appear to be more horizontal. It is shown that the present experimental setup is an improvement over the old setup because the frictional torque associated with the experiment has been reduced by 25 % approximately, and the ambient pressure reached in the chamber is a fourth of the ultimate pressure reached before.