This seminar will present foundation study results and introduce a new "S.E.C.R.E.T." (Shear Extension Combined Rheology Experimental Techniques) four year experimental fellowship project to expand our understanding of "kinematically mixed" rheological flows - those that contain simultaneous shear and extension.
The presenter 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 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 research, independent measurement of shear and extension rates in arbitrarily oriented flow fields appears surprisingly non-trivial and disconnected from our apparently well-defined shear and extension rates in the laboratory reference frame. There is one option at the present time for the experimental work, but from multiple discussions to date, no concrete or universally accepted solution. This is an important area for the field to rationalise if kinematically mixed flows are to be one day fully understood.
This seminar will be a brief, high level overview of both of these areas (circa 10-15 minutes of slides), after which depending on the audience interest, other sets of slides can be presented that expand on either of the above areas. Alternatively, informal discussion can be simply continued on either/both of these areas, or indeed any other areas from the presenter's work (see https://rshlab.com/), with the opportunity to continue post-seminar too.
Note that MR velocity imaging is a powerful tool for fluid dynamics work and suspension rheology in general. Depending on availability, colleagues from the Illinois biomedical imaging centre may be attending this seminar, presenting an opportunity to find out about local facilities and opportunities for this technique.
Dr Hodgkinson’s website can be found at Academic website of Dr Richard Hodgkinson (rshlab.com).
Host: Professors Charles Schroeder and Randy Ewoldt