Segregation-driven Patterns and Controlled Convection in Vertically Vibrated Binary Granular Mixtures


Meheboob Alam (Jawaharlal Nehru Centre for Advanced Scientific Research)


Unlike molecular fluids, segregation or demixing occurs spontaneously in driven granular mixtures of different size and/or density particles which can be a nuisance/blessing in processing industries dealing with granular materials. Understanding segregation-driven patterns and finding ways to control them remains a key challenge in granular physics research. I will discuss our recent experimental results on novel patterns displaying the coexistence of sub-harmonic and synchronous states and that of gas- and liquid-like states in experiments on vertically vibrated binary granular mixtures in a quasi-two-dimensional Hele-Shaw cell. The segregation of heavier and lighter particles along the horizontal direction is shown to be the progenitor of such phase-coexisting patterns. The phase diagram of all patterns has been identified, and a simple recipe to control ``buoyancy-driven'' granular convection is demonstrated. Theoretical challenges to predict such phase-coexisting patterns will be discussed. In the second part of this talk, I'll briefly outline an order-parameter theory for nonlinear granular convection in vibrated mono-disperse system.

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