Unpicking the SECRETs of kinematically mixed rheology with Shear Extension Combined Rheology Experimental Techniques

This flash presentation and poster presents foundation study results and introduces a new four year experimental research project to expand our understanding of "kinematically mixed" rheological flows - those that contain simultaneous shear and extension.

The author developed and proved a technique that allows us to study shear viscosity under not a conventional pure shear flow, but for the first time, one containing a simultaneous combination of shear and extensional deformation. This is relevant to flows of materials which show extension-aligning behaviour, from polymers to anisotropic particle suspensions. The results stand to inform fluid model development and validation towards improved prediction of complex, industrially-relevant flow fields.

The initial particle image velocimetry study (https://doi.org/10.1122/8.0000380) was limited to a transparent solution with a specific (refractive index matched) solvent composition. The new project - an EPSRC funded fellowship - will make a unique transformation. It will apply magnetic resonance velocity imaging, enabling the study of and providing exemplar data for a wide variety of systems, including opaque suspensions.

Coupled to this, independent measurement of shear and extension rates in arbitrarily orientated flow fields is surprisingly non-trivial and disconnected from our apparently well-defined shear and extension rates in the laboratory reference frame. Discussion is invited going forward towards clarifying this difficulty.