# Pattern formation in a fully-3D segregating granular flow

## TL;DR

This study investigates how size-based segregation patterns form in a fully three-dimensional spherical tumbler, revealing the roles of flow dynamics and particle interactions through experiments and modeling.

## Contribution

It introduces a combined experimental and continuum modeling approach to understand pattern formation in 3D granular flows, highlighting the influence of flow structures on segregation.

## Key findings

- Large particles accumulate in non-mixing islands.
- Flow structures influence pattern robustness.
- Chaotic regions affect particle segregation.

## Abstract

Segregation patterns of size-bidisperse particle mixtures in a fully-three-dimensional flow produced by alternately rotating a spherical tumbler about two perpendicular axes are studied over a range of particle sizes and volume ratios using both experiments and a continuum model. Pattern formation results from the interaction of size segregation with chaotic regions and non-mixing islands of the flow. Specifically, large particles in the flowing surface layer are preferentially deposited in non-mixing islands despite the effects of collisional diffusion and chaotic transport. The protocol-dependent structure of the unstable manifolds of the flow surrounding the non-mixing islands provides further insight into why certain segregation patterns are more robust than others.