Jet-induced jammed states of granular jet impacts

TL;DR

This study uses two-dimensional simulations to explore how granular jet impacts lead to jammed states, revealing differences in pressure and shear stress behavior near jamming transitions for frictional and frictionless grains.

Contribution

It provides new insights into the equations of state and flow behavior during granular jet impacts, highlighting the effects of friction and particle dispersity on jamming phenomena.

Findings

Pressure and shear stress diverge near jamming, with exponents smaller than in sheared systems.

Critical density decreases with increasing grain friction.

Effective friction constant varies with strain rate and particle dispersity, showing metastability in mono-disperse systems.

Abstract

The impacts of granular jets for both frictional and frictionless grains in two dimensions are numerically investigated. A dense flow with a dead zone emerges during the impact. From our two-dimensional simulation, we evaluate the equations of state and the con- stitutive equations of the flow. The asymptotic divergences of pressure and shear stress similar to the situation near the jamming transition appear for the frictionless case, while their exponents are smaller than those of the sheared granular systems, and are close to the extrapolation from the kinetic theoretical regime. In a similar manner to the jam- ming for frictional grains, the critical density decreases as the friction constant of grains increases. For bi-disperse systems, the effective friction constant defined as the ratio of shear stress to normal stress, monotonically increases from near zero, as the strain rate increases. On the other hand, the effective friction constant has two metastable branches for mono-disperse systems because of the coexistence of a crystallized state and a liquid state.