Ultrasonic interferometry: study of particle sedimentation in liquid

An ultrasonic interferometry method was designed to study sedimentation of particles in liquid. The method, based on A mode echography, measures the amplitude of ultrasonic waves reflected (echo E ₁) by a fixed interface I ₁ called the solid plate-sediment interface, formed when particles are sedimenting on a solid plate. The amplitude of the echo depends on mechanical properties of the three media (solid plate, sediment and suspension), on the thickness of the sediment, and on the presence of a second mobile interface I ₂ called the sediment-suspension interface. The authors compared the sedimentation rate (SR) of particles determined by this method with the SR measured in a cylindrical tube, of the same geometry as the ultrasonic measurement cell and with theoretical values of the sedimentation rate given by theoretical models. Good agreement was obtained.