The motions of particles in model suspensions subjected to a shear.

Note: p. 88, 89 skipped in manuscript (noted)A Couette-type apparatus has been designed in which the motions of model glass spherical and rod-shaped particles were examined, in a shear field and compared with the motions predicted theoretically. The hydrodynamic theory describing the rotational motion of spherical particles was verified experimentally. Observations were made on the collision mechanism of spherical particles and shown to differ from the postulated mechanisms. Collision frequencies were measured in suspensions of spheres and the values agreed with the calculated values within the experimental error. The rotational motion of rod-shaped particles was examined. The particles were shown to move in an orbit similar to that predicted for ellipsoids by Jeffery. The period of rotation was found to be less than the predicted value. The discrepancy is probably due to the fact that the particles were cylindrical. On extended exposure of the particle to the shear action it was found that the "orbital constant" tended to drift. There was, however, no tendency for the orbital constant to assume the value predicted by Jeffery’s hypothesis of minimum viscosity. The instantaneous orientation of rod-shaped particles in a suspension were examined for three different axis ratios. Distribution curves were plotted in one plane which showed that the distribution of orbits remained constant over a period of time thus confirming the hypothesis of Eisenschitz