# Visco-rotational shear instability of Keplerian granular flows

## TL;DR

This paper investigates the linear stability of viscous Keplerian granular flows using a rheological model, revealing an instability driven by shear rheology and differential rotation that impacts planetary rings and protoplanetary disks.

## Contribution

It introduces a new rheological instability mechanism in dense granular flows under Keplerian rotation, highlighting conditions for its onset.

## Key findings

- Instability occurs when viscosity grows faster than the square of shear rate.
- The instability influences the dynamics of planetary rings.
- It may affect granular flows in protoplanetary disks.

## Abstract

The linear stability of viscous Keplerian flow around a gravitating center is studied using the rheological granular fluid model. The linear rheological instability triggered by the interplay of the shear rheology and Keplerian differential rotation of incompressible dense granular fluids is found. Instability sets in granular fluids, where the viscosity parameter grows faster than the square of the local shear rate (strain rate) at constant pressure. Found instability can play a crucial role in the dynamics of dense planetary rings and granular flows in protoplanetary disks.