Experimental analysis of basal wall friction coefficient for a velocity controlled confined granular flow

National Taiwan University, Department of Mechanical Engineering, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 1 December 2025

Abstract

This work presents a novel experimental design to measure the effective wall friction coefficient μ_w between a confined granular material and a flat wall under a controlled relative velocity and normal load, with concurrent monitoring of the solid volume fraction of the interacting layer. The design allows us to investigate the effects of initial packing configuration, in random or face-centered-cubic packing. The μ_w is further scaled by the particle-wall pure sliding friction coefficient, μ_pw, with the normal load considered to infer the degree of incoherent particle dynamics when discrete particles may develop rolling but not pure sliding contacts. Reverse μ_w/μ_pw variation trends with the sliding velocity are found and explained.