Transport mechanism in a photoelastic chute flow in view of the evolution of force networks

This work adopts high-speed imaging analysis to measure the flow dynamics and the force chain properties for steady chute flows of photoelastic circular disks with fast-changing fringe patterns. We adopt the granular kinetic theory to evaluate collision-based stress components while calibrating the fringe-based force chain properties to evaluate the friction-based stress components. The fringe images allow us to define a new penetration band to clarify the spatial extent of pure-collisional and pure-frictional transport and a possible transition in the mid-layer, within which grain rotation is promoted, which may be associated with the breaking of the force network. Superposition of the collision- and the friction-based stress evaluation does not recover the hydrostatic depth profiles, highlighting an unaddressed transport mechanism or deficiency in the measurement technique.