# The influence of surface roughness on the rheology of immersed and dry frictional spheres

## TL;DR

This study investigates how surface roughness affects the rheological behavior of frictional spheres in both immersed and dry conditions, revealing that roughness influences jamming but not the effective friction coefficient.

## Contribution

It provides new insights into the role of surface roughness on jamming and rheology, showing similar effects in immersed and dry states and enabling data collapse through rescaling.

## Key findings

- Critical volume fraction at jamming decreases with roughness.
- Effective friction coefficient remains largely unaffected by roughness.
- Rheological data collapse onto master curves when rescaled.

## Abstract

Pressure-imposed rheometry is used to examine the influence of surface roughness on the rheology of immersed and dry frictional spheres in the dense regime. The quasi-static value of the effective friction coefficient is not significantly affected by particle roughness while the critical volume fraction at jamming decreases with increasing roughness. These values are found to be similar in immersed and dry conditions. Rescaling the volume fraction by the maximum volume fraction leads to collapses of rheological data on master curves. The asymptotic behaviors are examined close to the jamming transition.