The effect of nonvertical alignment on the performance of a falling-cylinder viscometer

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Abstract
It is found that when an unguided cylinder falls through a newtonian fluid in a viscometer tube inclined from the vertical the cylinder falls with an increased speed compared with the speed of fall in the vertical position. At an angle of about 15° from the vertical, a cylinder may travel at more than twice its vertical speed. This phenomenon is investigated experimentally, and a theory is derived which shows that the change in fall time is due to the cylinder falling eccentrically in the tube. When the viscometer tube was tilted, a maximum reduction in fall time of 59±2% was produced, which compares well with a theoretical value of 584%. The relationship between viscometer tube angle and the eccentricity of the falling cylinder is deduced from the analysis. This relationship is verified experimentally.