ULTRASONIC VELOCITY AND ATTENUATION OF GLASS BALLOTINI IN VISCOUS ANDVISCOELASTIC FLUIDS

Measurements are reported of the attenuation, alpha, and the velocity, c, of 1-5 MHz compressional wave ultrasound in suspensions of glass b allotini in Newtonian and non-Newtonian base fluids. For the Newtonian fluids, good agreement is found between the measured alpha and c, and the alpha and c obtained from the Urick and the Ament expressions, us ing the same value for the base fluid's viscosity. For the non-Newtoni an base fluids, this agreement was absent. The existence of shear elas ticity G in these fluids is suggested to explain the results. By incor porating elasticity into the Urick and the Ament theories the disagree ment is resolved, and values of G are found which are in order-of-magn itude agreement with those found at the same frequency by another meth od. A test is proposed of a recent assertion that simple molecular flu ids possess a shear elasticity.