Please use this identifier to cite or link to this item: http://hdl.handle.net/10603/429216
Title: Rheology of dense granular materials
Researcher: Dsouza, Peter Varun
Guide(s): Nott, Prabhu R
Keywords: Engineering
Engineering and Technology
Engineering Chemical
University: Indian Institute of Science Bangalore
Completed Date: 2021
Abstract: Granular materials are frequently encountered in our daily lives and are widely used in several industrial processes. Characterising the flow of these materials has always proved challenging due to the lack of simple measurement techniques. Recent work in our group has shown that when granular materials are slowly sheared in a cylindrical Couette device, a standard rheometer accessory, they exhibit an anomalous rheological behaviour. It was shown that all components of stresses measured increased exponentially with depth. In comparison, the stress for a static column of grains saturates with depth. It was further shown that this behaviour could be explained by the presence of a toroidal vortex that spans the entire system. It was proposed that such a vortex was driven by shear-induced dilation or dilatancy, a property of granular materials that has no analogue in fluids. Dilatancy is the decrease in density is regions of shear and is a consequence of rigid granular particles requiring free volume to move. In this work, we ask if dilation is indeed the origin of this vortex and the anomalous stress profile. We test the validity of these claims, first by replicating and validating these results and then checking for the robustness of the vortex flow. We then ask how general the effect of dilation is by testing a more complicated flow namely, the flow in a split-bottom Couette device, a variation of the cylindrical Couette device. In this device, shear originates from the boundary between a moving and stationary base plate. We then show that we get a variety of dilation-driven vortices that have similar features as the vortex observed in the cylindrical Couette device. Despite this effect that dilatancy has on generating these vortices, all constitutive models treat steady granular flows as incompressible and, thus, ignore dilation. We therefore propose an extension to a well-known constitutive model for slow granular flows, the critical state plasticity model. We propose that the deformation at a point is depend...
URI: http://hdl.handle.net/10603/429216
Appears in Departments:Chemical Engineering

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01_title.pdfAttached File162.8 kBAdobe PDFView/Open
02_prelim pages.pdf374.46 kBAdobe PDFView/Open
03_table of contents.pdf95.17 kBAdobe PDFView/Open
04_abstract.pdf47.8 kBAdobe PDFView/Open
05_chapter 1.pdf194.65 kBAdobe PDFView/Open
06_chapter 2.pdf1.31 MBAdobe PDFView/Open
07_chapter 3.pdf5.57 MBAdobe PDFView/Open
08_chapter 4.pdf455.45 kBAdobe PDFView/Open
09_chapter 5.pdf929.5 kBAdobe PDFView/Open
10_annexure.pdf498 kBAdobe PDFView/Open
80_recommendation.pdf313.68 kBAdobe PDFView/Open
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