|Date: Friday, September 27, 2019
Location: 1084 East Hall (3:00 PM to 4:00 PM)
Title: Levitating granular cluster: typical behavior and noise-induced rare events
Abstract: Granular matter is ubiquitous in nature and exhibits a variety of nontrivial phenomena. In addition, granular medium is intrinsically far from equilibrium, as particles collide inelastically, and a continuous energy input is required to ensure a steady state. Within the same system, different regions of granular media can be at a solid or a gas phase. Here we focus on a granular Leidenfrost effect: a solid-like cluster is levitating above the "hot" granular gas . This state was observed experimentally, when granular matter was vertically vibrated in a two-dimensional container . The solid-gas coexistence can be described by using granular hydrodynamics with the properly measured transport coefficients . We performed extensive molecular dynamics simulations of a simple model of inelastic hard spheres driven by a "thermal" bottom wall. Simulations showed that for low wall temperatures, the levitating cluster is stable, while for high wall temperatures, it breaks down, and the hot gas bursts out resembling a volcanic explosion . We found a hysteresis: for a wide range of bottom wall temperatures, both the clustering state and the broken state are stable. However, even if the system is at the (stable) clustering state, a "volcanic explosion" is possible: it is a rare event driven by large fluctuations. We used techniques from the theory of rare events to compute the mean time for cluster breaking to occur; this required the introduction of a two-component reaction coordinate .
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Speaker: Evgeniy Khain
Institution: Oakland University
Event Organizer: Silas Alben firstname.lastname@example.org