Geometry of Fluid Interfaces
AG Prof. Dr. Ralf Seemann

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Control of pore-scale interfacial advance for Newtonian and complex fluids by the interplay of fluid properties and pore-throat geometry

We use microfluidic techniques to study local front advance of immiscible multiphase flow in artificial porous media with applications e.g. in enhanced oil recovery. Therefore, we use quasi two-dimensional Hele-Shaw cells decorated with arrays of pillars having circular or angular cross-sections to mimic the relevant features of natural porous media such as sandstone.

At low capillary numbers, in the quasi-static limit, the displacement mechanism for interfacial front advance is dominated by capillary forces and can be categorized in three fundamental classes of local interfacial instabilities, i.e. two non-cooperative instabilities such as burst and touch events (Fig 1a,b) and cooperative overlap events (Fig. 1c,d). In particular, we study the mutual impact of pore-throat geometries as defined by the different pillar arrays and the impact of wettability on the relative frequency of cooperative and non-cooperative interfacial instabilities and the resulting interfacial advance.

Fig.1:: Optical micrographs of meniscus instabilities in a Hele-Shaw cell decorated with an array of cylindrical obstacles for different wall wettability: (a) burst, (b) touch, (c) overlap where the three phase contact lines touch first, and (d) overlap where the fluid-fluid interfaces touch first.

At increased capillary numbers, i.e. for higher flow-rates, we aim at understanding the impact of viscosity ratio of invading and defending phase on the relative distribution of cooperative instabilities. Additionally, we increase the complexity of the invading fluid using viscoelastic aqueous polyacrylamide solutions of high molecular weight. Here, we are interested to understand the role of elasticity and shear-thinning on the displacement process.

Group members on this project: Dr. Michael Jung, Pegah Shakeri, Prof. Dr. Ralf Seemann

External collaborations: Dr. Martin Brinkmann (Northumbria), Prof. Dr. Stephan Herminghaus (MPI-DS)