| Popis: |
Measurements are reported of the attenuation, α, and the velocity, c , of 1–5 MHz compressional wave ultrasound in suspensions of glass ballotini in Newtonian and non-Newtonian base fluids. For the Newtonian fluids, good agreement is found between the measured α and c , and the α and c obtained from the Urick and the Ament expressions, using the same value for the base fluid's viscosity. For the non-Newtonian base fluids, this agreement was absent. The existence of shear elasticity G in these fluids is suggested to explain the results. By incorporating elasticity into the Urick and the Ament theories the disagreement is resolved, and values of G are found which are in order-of-magnitude agreement with those found at the same frequency by another method. A test is proposed of a recent assertion that simple molecular fluids possess a shear elasticity. |
