SOUND-PROPAGATION IN SUSPENSIONS AND ACOUSTIC IMAGING OF THEIR MICROSTRUCTURE

Ultrasound, as a technique for interrogating two-phase mixtures, has t he advantages of being non-intrusive, it has good temporal resolution, and can be made to penetrate typically opaque, highly concentrated mi xtures without resorting to acoustic impedance matching. Sound propaga tion characteristics in a mixture depend on the size of the particles, their concentration, the material properties of the two phases, and a re sensitive to the wavenumber, k = 2pi/lambda, of sound. A combined t heoretical and experimental investigation was conducted to quantify at tenuation and sound speed in mono-disperse mixtures to provide a quant itative framework to interpret acoustic data and extract information o n the microstructure of flowing, very concentrated solid-liquid mixtur es. This paper builds upon this work to identify the role of microstru cture on acoustic propagation in suspensions, in the limit of long wav elengths, and the results are then used to choose suitable operating f requencies to image a liquefaction event in a bed of 50 mum glass bead s in water.