Dr Indresan Govender, UCT Physics & Centre for Minerals Research, will give a talk... Fri, 26 September 2014, 13:00 to 14:00 Duncan Elliott Seminar Room, RW James Building A new visco-plastic rheology for granular flows Recently Jop et al. (2006) proposed a seminal insight into the rheology of dense granular flows. The resulting constitutive law employed a new dimensionless number − the inertial number: I = γ d / √P/m where d is the particle size, γ the local shear rate, P the confining pressure and ρm the material density − that solely governs the visco-plastic nature of granular flow. The next decade revealed that the rheology is severely limited to unidirectional flows and a narrow regime of inertial number. Consequently, most real granular flows − like those encountered in industrial tumbling mills, and minerals processing in general − do not conform to the rheology of Jop et al. (2006). Our work takes genesis from this limitation and aims to generalise the constitutive relations with a more predictive model of tumbling mill rheology. We show that by combining the ideas of Jop et al. (2006) with kinetic theory arguments from Bagnold (1954) that are supported by Positron Emission Particle Tracking (PEPT) measurements, we successfully recover the underlying constitutive law (actually, its invariant form) for the multi-directional flows in rotating drums that is consistent with the full tensorial description of Cortet et al. (2009). In this talk I will: • Make plain what rheology means and advocate a holistic approach that researchers should follow. • Describe key outputs from PEPT and it’s profound impact on modelling. • Present a new rheology of granular flow that underpins ALL research involving macroscopic grains, and potentially granular suspensions.
Posted on: Tue, 23 Sep 2014 05:36:09 +0000
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