Prof. Baruch Meerson

Function

Visiting professor

Personal Website

http://www.phys.huji.ac.il/~meerson/

Info

The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem 91904, Israel

Publications

Close-packed granular clusters: hydrostatics and persistent Gaussian fluctuations

Granular Matter, 10, 21-27

(2007)

Research Projects
Abstract

Dense granular clusters often behave like macro-particles. We address this interesting phenomenon in a model system of inelastically colliding hard disks inside a circular box, driven by a thermal wall at zero gravity. Molecular dynamics simulations show a close-packed cluster of almost circular shape, weakly fluctuating in space and isolated from the driving wall by a low-density gas. The density profile of the system agrees very well with the azimuthally symmetric solution of granular hydrostatic equations employing constitutive relations by Grossman et al., whereas the widely used Enskog-type constitutive relations show poor accuracy. We find that fluctuations of the center of mass of the system are Gaussian. This suggests an effective Langevin description in terms of a macro-particle, confined by a harmonic potential and driven by delta-correlated noise. Surprisingly, the fluctuations persist when increasing the number of particles in the system.

Materials
 

Giant fluctuations at a granular phase separation threshold

Physical Review E, 69, 021302

(2004)

Research Projects
Abstract

Granular hydrodynamics is tested in a system of nearly elastically colliding hard spheres driven by a thermal wall. If the aspect ratio of the confining box exceeds a threshold value, granular hydrodynamics predicts phase separation and formation of a localized almost densely packed domain. Event-driven molecular dynamic simulations confirm this prediction. However, the hydrodynamic bifurcation curve agrees with the simulations quantitatively only well below and well above the threshold. In a wide region of aspect ratios around the threshold the system is dominated by fluctuations, and granular hydrodynamics fails to give an accurate description.

Materials
 

Close-Packed Floating Clusters: Granular Hydrodynamics Beyond the Freezing Point?

Physical Review Letters, 91, 024301

(2003)

Research Projects
Abstract

Monodisperse granular flows often develop regions with hexagonal close packing of particles. We investigate this effect in a system of inelastic hard spheres driven from below by a „thermal“ plate. Molecular dynamics simulations show, in a wide range of parameters, a close-packed cluster supported by a low-density region. Surprisingly, the steady-state density profile, including the close-packed cluster part, is well described by a variant of Navier-Stokes granular hydrodynamics (NSGH). We suggest a simple explanation for the success of NSGH beyond the freezing point.

Materials