Mathematikgebäude, Seminarraum M614/616 (6. Etage)

A common problem in multi-layer shear flows, especially from the perspective of process engineering, is the occurrence of interfacial instabilities. For purely viscous fluids 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. Nonlinear 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. Theseare 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 such as visco-plastic sculpting and large droplet encapsulation.

Prof. Dr. Sarah Hormozi

Ohio University