Seminar - Bjornar Sandnes - Displacement structures in multiphase frictional flows
Wednesday 30 March 2011, 4.00 pm - 5.00 pm
Civil Engineering Conference Room
Dr. Bjornar Sandnes
University of Oslo
We study the displacement dynamics of settling granular mixtures, where inter-particle friction plays a central role. Such ‘frictional fluids’ are ubiquitous in nature and engineering. For example, they play a key role in landslides, where fluidisation causes the rheology to jump rapidly from solid- to fluid like behavior. Of interest in engineering applications is the role of frictional granular mixtures in oil and gas recovery and potentially for processes linked to CO2 geo-sequestration. Here we consider Coulomb friction and compressibility in the fluid dynamics of confined flows, and discover surprising responses including intermittency and a transition to quasi-continuous dynamics. Moreover, by varying the injection rate over several orders of magnitude, we characterize new dynamic modes ranging from stick slip bubbles at low rate to destabilized viscous fingers at high rate. We classify the fluid dynamics into frictional and viscous regimes, and present a unified description of emerging morphologies in granular mixtures in the form of extended phase diagrams.
Bjornar Sandnes received his Ph.D. from the Department of Physics, University of Oslo in 2004. A postdoc period in the Advanced Materials and Complex Systems Group (UiO) followed, and included a visiting period at the School of Chemical and Biomolecular Engineering, University of Sydney in 2007. In 2008 Bjornar was appointed as a Research Fellow at the Optical Biomedical Imaging and Sensing Group at Macquarie University. Later in 2008, he was awarded a personal fellowship by the Norwegian Research Council, and has since worked for the University of Oslo, while being located in Sydney and working as a visiting associate at both School of Chemical and Biomolecular Engineering (USyd) and Macquarie University.
Bjornar has a diverse research background that includes flow behaviour and pattern formation in complex fluids, photonics and biomedical imaging, fluorescent nanoparticles as biolabels, thermal and PV solar energy systems and phase change materials for energy storage.