Abstract
Ranjini Bandopadhyay: „Scaling laws obtained in experiments on rising Brazil nuts and aging colloidal suspensions”
Raman Research Institute, Bangalore, India
In this talk, I shall discuss two recent experiments. The first experiment studies the Brazil-nut effect in which a large intruder particle, immersed in a vertically shaken bed of smaller particles, rises to the top even when it is much denser. Granular convection, void-filling mechanisms and even air drag can influence this effect. In our experiments, we use high-speed imaging to extract the rise-time of an intruder over a range of vibration parameters, intruder densities and diameters, and bed aspect ratios. We uncover a scaling law for the rise of the intruder in the granular convection-driven regime. In the second experiment, we employ Dynamic Light Scattering to study the dynamic slowing down in soft glassy nanoclay suspensions. We measure the primary (α) and the secondary (β) relaxation processes of these suspensions and propose a one-to-one mapping between the waiting time (tW) of these aging suspensions and the inverse of the thermodynamic temperature (1/T) of a supercooled liquid. In this framework, we demonstrate the coupling between the α and the β-relaxation processes and the self-similar nature of these dynamics upon changing the concentration of the suspension.