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Visco-plastic lubrication: from theory to application

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A common problem in multi-layer shear flows, especially from the perspective of process engineering, is the occurrence of interfacial instabilities. For purely viscous fuids these occur at low Reynolds numbers. However, multi-layer duct flows can be stabilised by astute positioning of a visco-plastic fluid as the lubricant that remains unyielded at the interface. This technique has been termed visco-plastic lubrication. In this talk, I will start with an introduction to Visco-Plastically Lubricated (VPL) flows. Then I will present the results of a systematic study aimed at extending visco-plastic lubrication from a theoretical concept towards more industrial applications. The results come in two parts. Firstly, a computational study of VPL flows will be presented in the setting of a Newtonian core fluid surrounded by a Bingham lubricating fluid, within pipe and channel configurations. Flow development and start-up are explored. Non-linear perturbations are also studied to obtain better understanding about the stability of these flows, e.g. what role does the unyielded plug play, do perturbations remain concentric or develop asymmetries, how large an amplitude of perturbation can be withstood and at what flow rate. These are essential questions for industrial prototyping. Secondly, I will show the feasibility of VPL flows with viscoelastic core fluids from both experimental and theoretical perspectives. Viscoelastic fluids are frequently used in the polymer and food industries, which are large areas for application. I will close by connecting visco-plastic lubrication to potential novel applications in stable core-annular oil pipelining, in manufacturing and in droplet encapsulation.

Biography: Sarah Hormozi is a Postdoctoral Fellow at the Universite Paris Est, Laboratoire Navier. Her postdoctorate is sponsored by the Natural Sciences and Engineering Research Council of Canada (NSERC). Sarah completed her Ph.D. in Mechanical Engineering from the University of British Columbia in 2011. Her research interests mainly lie in the broad field of non-Newtonian fluid mechanics, ranging from computation to experiment to theory. She has authored around 20 journal and conference publications in the area of fluid mechanics. Sarah is the recipient of both industrial and academic Post-Doctoral Fellowships from NSERC . At UBC , Sarah served as Instructor and Teaching Assistant for several courses in Mechanical Engineering and Applied Mathematics Departments, and also as the manager of Complex Fluid Laboratory. She will be joining the faculty at the Ohio University this coming fall.

This talk is part of the Fluid Mechanics (DAMTP) series.

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