Real-time analysis of the growth of granular media by an ultrasonic method: Application to the sedimentation of glass balls in water

In this work, we propose a real-time analysis of the growth of a granular material by a high frequency ultrasonic method (around 5 MHz) based on normal incidence reflectometry. This method is non-destructive. It can be applied to the general case of cloudy solutions in optically opaque sedimentation cells. Results were obtained on glass balls used as a model granular material. Glass balls were sedimenting in water. Measurement of the deposit thickness (varying from several dozen of micrometers to several millimeters) leads to morphological and dynamic properties such as the volume solid fraction and the deposit growing rate. The strong influence of the particle size distribution (median diameter, broadness of the size distribution) on the dynamic properties of the particle packing was determined quantitatively. Our results are in good agreement with the classical model of sedimentation for an isolated sphere (Stokes law).