The aerodynamic resistance to a sphere rotating at high speed

Abstract
An attempt has been made to adapt the technique of magnetic suspension of steel rotors to the study of high-speed aerodynamic problems. Surface speeds up to ca. 800 m/s are possible. The advantages and shortcomings of the technique from the aerodynamic point of view are discussed together with the different regimes of flow at present attainable with the apparatus. The particular case of a rotating sphere in the boundary-layer regime is considered and some results obtained with this technique are presented. Observations with smoke and with schlieren photographs show that the gas flows from the poles to the equator where it is thrown off as a narrow plane radial jet. These results are in accord with Howarth’s theoretical predictions. The measured drag torque on the sphere is however somewhat higher than the predicted value and possible reasons for this are considered. The work is now being extended to other regimes of flow.

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