Observation of aspherical particle rotation in Poiseuille flow via the resistance pulse technique. II. Application to fused sphere ``dumbbells''

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Abstract
The presence of an insulating particle in an electrolyte‐filled pore causes a fractional resistance change, ΔR / R = fv / V, where v / V is the ratio of particle to pore volume. The shape factor f is a function of particle shape and orientation. While traversing the pore, the particles will rotate in the shear of Poiseuille flow. As a result aspherical particles will exhibit periodic resistance variations and this effect has been observed directly using fused sphere ``dumbbells'' as test particles. The particle dynamics are found to be in agreement with simple hydrodynamic theory. The resistance effects for the dumbbells can be described in terms of an equivalent ellipsoid with an axis of symmetry to equatorial axis ratio of 1.25. On the other hand, the dumbbells are hydrodynamically well described in terms of an ellipsoid with an axis ratio of 2.4. The data indicate that strong orientation effects occur in the convergent entrance flow.

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