Granular buoyancy in the context of segregation of single large
grains in dense granular flows
Abstract: Modelling of particle-size segregation in dense granular
flows could benefit from a better understanding of the segregation
behaviour of an isolated large particle in a flow of smaller grains.
In one previous study, the force along the direction of segregation
experienced by such an intruder particle was measured and decomposed
into a modified Archimedean buoyancy force and a segregation lift
force. Here we present a micro-mechanical analysis of this new
granular buoyancy force in order to connect the micro-scale contact
behaviour to the macroscopic force. In doing so we uncover evidence
that links the magnitude difference between buoyancy and gravity
acting on large intruders to a decrease in surface contact density.
Our findings reveal micro-scale insights into buoyancy in dense
granular flows; support the use of the Voronoi approximation for
calculation of the buoyancy force; and substantiate a specific force
decomposition into buoyancy and segregation lift forces. Ultimately,
these insights are expected to impact development of models for size
segregation by linking micro and macro behaviour.
Relevance to industry: This work studies the forces on a single large
grain in a mixture of smaller grains, such bidisperse granular
mixtures with a low large particle concentration are abundant in
Kasper van der Vaart obtained a bachelor in physics in Amsterdam and a masters in Nanomaterials in Utrecht. He did his promotion at the EPFL on the topic of granular materials, after which he went to Stanford for a postdoc on the topic of collective swarming behaviour. Now he is back in the Netherlands as a postdoc in the Multi-scale mechanics group at the University of Twente.