Analysis on the Motion of Particles Agitated by Ultrasound and Immersed in a Host Medium, with Application to Viscosity Measurement

Glass spherical particles (mean diameter of 250 μm), immersed in a liquid host medium with a controlled temperature of 30 °C, were agitated by a 2.7 MHz ultrasonic pumping wave during 990 ms. A probing wave of 10.0 MHz continuously radiated the particles and from the power spectrum of the scattered wave, the time-decay of the particle ensemble mean squared velocity was determined following the switching off of the pumping transducer. This time-decay is shown to be proportional to the host medium viscosity. Degassed distilled water was used as a calibrating medium. The method was tested using two mixtures of glycerin and degassed distilled water and a sample of human blood plasma. The measured viscosity, within the range of 15·10⁻⁴Nsm⁻² to 43·10⁻⁴Nsm⁻², presented an error less than 8.0% when compared with the results obtained by different methods.