Still water: dead zones and collimated ejecta from the impact of granular jets

TL;DR

This study investigates the impact of dense granular jets on targets, revealing that the resulting ejecta cone angle remains consistent regardless of target shape or dissipation details, due to flow behavior akin to perfect fluids.

Contribution

The paper demonstrates that granular jet impact dynamics produce a universal ejecta cone angle, independent of target shape and dissipation mechanisms, through experiments, simulations, and continuum modeling.

Findings

Ejecta cone angle is insensitive to target shape.

Flow behavior resembles that of perfect fluids despite dissipation.

Granular impact dynamics produce a universal ejecta pattern.

Abstract

When a dense granular jet hits a target, it forms a large dead zone and ejects a highly collimated conical sheet with a well-defined opening angle. Using experiments, simulations, and continuum modeling, we find that this opening angle is insensitive to the precise target shape and the dissipation mechanisms in the flow. We show that this surprising insensitivity arises because dense granular jet impact, though highly dissipative, is nonetheless controlled by the limit of perfect fluid flow.