Kinetic granular temperature and its measurement using speckle visibility spectroscopy

Abstract The occurrence of a mesoscopic scale in granular materials leads to a sharp increase in the number of interaction processes at both intra- and inter-scale levels. The mesoscopic scale is the main source of the complex macroscopic properties of granular materials. The quantification of mesoscopic disordered movements is often referred to as granular temperature. In this paper, we first introduce the physical meaning of the original granular temperature of a kinetic nature, Tk, and then briefly summarize the advances made over the past few decades. Our research group has focused on Tk measurement using speckle visibility spectroscopy. The principle of this technique and the instruments developed in our research group are briefly introduced. Our work shows great promise in the measurement of kinetic granular temperature. Finally, a summary of granular temperature and some recent developments in speckle visibility spectroscopy measurements are presented.