Falling Sphere Viscometry. II. End Effects in Short Tubes

Abstract

Stokes' law for determining viscosity from sphere fall velocity applies in the absence of wall, inertial, and end effects. One objective of this investigation was to establish a criterion for choosing a tube long enough to avoid end effects. The resulting criterion is as follows. For L/D=2 and d/D<0.125 there are no observable end effects throughout the middle third of the fall tube, even for Re as large as 2. Another objective was to establish a correlation of simultaneous wall and end corrections to Stokes' law in the absence of inertial effects, for application in short tube viscometry. The desired correlation is presented in Figure 3 and Table I.