New patterns in high-speed granular flows

TL;DR

This paper presents new high-speed granular flow patterns discovered through extensive simulations, revealing complex structures, scaling laws, and challenging existing rheological models.

Contribution

It introduces novel flow regimes in high-speed granular flows, characterized by complex internal structures and a new scaling law for mass flow rate.

Findings

Emergence of complex flow patterns with secondary flows and symmetry breaking

Existence of steady 'supported' flows with dense core and energetic granular gas

Flow regimes obey a scaling law relating mass flow rate to holdup

Abstract

We report on new patterns in high-speed flows of granular materials obtained by means of extensive numerical simulations. These patterns emerge from the destabilization of unidirectional flows upon increase of mass holdup and inclination angle, and are characterized by complex internal structures including secondary flows, heterogeneous particle volume fraction, symmetry breaking and dynamically maintained order. In particular, we evidenced steady and fully developed "supported" flows, which consist of a dense core surrounded by a highly energetic granular gas. Interestingly, despite their overall diversity, these regimes are shown to obey a scaling law for the mass flow rate as a function of the mass holdup. This unique set of 3D flow regimes raises new challenges for extending the scope of current granular rheological models.