Role of defects in the onset of wall-induced granular convection

Abstract

We investigate the onset of wall-induced convection in vertically vibrated granular matter by means of experiments and two-dimensional computer simulations. In both simulations and experiments we find that the wall-induced convection occurs inside the bouncing bed region of the parameter space in which the granular bed behaves like a bouncing ball. A good agreement between experiments and simulations is found for the peak vibration acceleration at which convection starts. By comparing the results of simulations initialised with and without defects, we find that the onset of convection occurs at lower vibration strengths in the presence of defects. Furthermore, we find that the convection of granular particles initialised in a perfect hexagonal lattice is related to the nucleation of defects and the process is described by an Arrhenius law.

Transport Properties and Segregation Phenomena in Vibrating Granular Beds

“…Many researchers have studied the dynamics of dry granular systems (Fortini and Huang, 2015;Hsiau et al, 2011;Knight et al, 1996;Tai and Hsiau, 2004). However, the flow behavior and dynamic properties of wet granular materials have received less attention.…”

“…Klongboonjit and Campbell (2008) completed a soft-particle recreation, in which convection strength was usually augmented with particle stiffness, as well as upon reaching a maximum value, the convective strength then decreases even with the further increase of particle stiffness. Fortini and Huang (2015) discovered that wall-induced convection happens within the bouncing bed region of the parameter's space, within which the granular bed acts similarly to a bouncing ball. The original bed height can be non-dimensionalized by dividing it by bead diameter d, resulting in H = h/d.…”

Radar for tracer particles

“…Despite of their ubiquity in nature, industries and our daily lives, describing granular materials as a continuum, particularly in the vicinity of the transition from a solidlike to a liquidlike state, is still far from trivial 9 . With the help of computer simulations, we can predict to a certain extent the collective behaviors of granular materials, such as convection, agglomerations, silo blockage, mixing and segregations [10][11][12] . At the particle level, a direct comparison of the predicted trajectories of computer simulations to experiments is always desirable to verify the model employed.…”

Density-wave fronts on the brink of wet granular condensation

“…To face this challenge, it is indispensable to explore instabilities in granular matter driven far from thermodynamic equilibrium. From Faraday crispations and heaping [19][20][21] to sand dunes and ripples 22,23 , from convection [24][25][26][27] to segregation [28][29][30] , from parametric wave patterns such as strip, square and hexagons [31][32][33] to localized excitations 34,35 , from spiral patterns 36 to kink fronts 37,38 , agitated granular matter has been demonstrated to be a rich pattern forming system. Understanding the emerging time and length scales at criticality using nonlinear dynamics approaches and numerical simulations has also advanced out understanding of granular dynamics from a different perspective [39][40][41] .…”