Rotations, collisions and orientations in model suspensions.

Particles in liquid suspensions subjected to velocity gradients undergo characteristic rotational and translational motions. The rotations are superimposed upon the translational motions, thus causing the particles to undergo "cart wheel" or rolling movements. The type of rotational motion described by a particle is characteristic of its shape; the rotations are periodic and in the case of elongated particles result in preferred orientations. The two types of motion are of considerable interest in connection with viscosity thixotropy, flow anisotropy, particle aggregation etc., in solutions of macromolecules, colloidal sols and suspensions of large particles