Direct and indirect measurements of the rheological property of steady dry granular flows down a rough incline
Date Issued
2015
Date
2015
Author(s)
Chiu, Ting-Yan
Abstract
The dynamics and rheological properties of dry granular inclined steady flows of nearly identical polydisperse spheres down a rough inclined chute are investigated through systematic experiments in this thesis. Direct force measurements via normal and shear normal cells are conducted at both the chute base and one lateral wall so that bulk basal and wall friction coefficients, μ and μw, are captured. To extract internal friction, indirect measurement based on quasi-two-dimensional control volume analysis of bulk stream-wise momentum is performed. In this analysis, the body force and assumed hydrostatic normal pressure are input from the basal normal load cell signal and so does the friction from the lateral frictional walls so that the only unknown is the tangential stress at a specific flow heights. Such indirectly measured internal friction and that from load cell measurements are examined with respect to bulk inertial number I. In calculating I, different estimations of an effective bulk shear strain rate were attempted for the current non-uniform flow. For the direct or indirect μ and all the estimated I, a rather robust trend that increases nonlinearly and monotonically with I is observed. However, the data using local μ and I possess greater dispersion from that use bulk averaged properties which poses questions to the feasibility of capturing local rheological property with mean flow properties.
Subjects
inclined granular flow
force measurement
control volume analysis
inertial number
friction coefficient
wall effect
μ-I law
Type
thesis