The retarding wall effects on the rolling motion of a descending sphere in a liquid contained in an inclined tube have been measured when the tube diameter is just larger than the diameter of the sphere. In the temperature range 353.15 – 463.15 K, the experimental data for the parameter K (the drag coefficient multiplied by the Reynolds number) were in much better agreement with the Lewis equation than with other proposed equations. For a d/D ratio of more than 0.707 the values of K in the Stokes region for a sphere diameter giving Reynolds numbers between 336 and 2285 were virtually the same.
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