The rheology of suspensions of rod-like and spherical particles and ultrasonic investigations of viscoelastic fluids

Suspensions of spherical particles in a second-order fluid are investigated. The technique of volume averaging is used to model the suspensions and experiments are performed on suspensions in the volume fraction range ;The rheology of suspensions of rod-like particles are investigated by adapting the technique of falling ball rheometry. It is found that this technique provides a useful and unique tool for studying randomly oriented suspensions. The results compare remarkably well with available theory, molecular dynamic modeling of rod-like macromolecules, and experiments on solutions of rod-like macromolecules. An extended dilute regime is discovered that has not been previously observed. It is found that as the diameter of the falling ball becomes small relative to the length of the rods the apparent viscosities of the suspensions decrease dramatically. A similar phenomena is found in highly concentrated suspensions of spheres. This decrease in the suspensions of rods and spheres superimpose when normalized and the normalization identifies a characteristic dimension for the rods which is between the length and the diameter. A falling ball apparatus that uses an eddy current detection method to measure the terminal velocity of the falling ball is also described.;The effect of viscoelasticity on the propagation of a finite amplitude planar acoustic wave is reported. Theoretical results indicate that viscoelasticity alters the form of harmonic waves generated in the fluid and may dramatically increase or decrease the amplitude. Experiments on aqueous solutions of polyethylene oxide and polyacrylamide support the theoretical results and suggest an explanation for shifts in the noise spectrum associated with cavitation.