Numerical assessment of the penetroviscometer approach for large, rapid and transient shear deformations (2007.13619v1)

Abstract: The rheological characterisation of complex fluids is mostly performed under simple shear flow in rotational rheometers. Their modern commercial versions are extremely sensitive instruments which are able to provide very accurate measurements of low values of different material functions, such as viscosity, viscoelastic moduli, etc., under certain ideal flow conditions. Nevertheless, they fail in providing reliable data when characterising the response of complex fluids at short time scales, due to artefacts induced by either instrument or fluid inertia. This is crucial in the analysis of the rheological properties of new formulations of shear thickening fluids specifically developed for protective applications, in which the performance is extremely linked to the time dependent structural changes provoked by the sudden impact loads. Thus, the necessity of providing a reliable experimental tool able to impose large, rapid, transient shear deformation for their rheological characterisation in conditions similar to those of the applications becomes evident. This numerical study aims at assessing the potential use of the penetroviscometer for the measurement of the transient shear viscosity of complex fluids at short time scales beyond the current limits of commercial rotational rheometers.