Finite Element Analysis of Vane Geometry for Shear Thinning Materials

Various materials such as cellulose nanofibers (CNF) suspensions contain non-isotropic structures that can lead to strong shear thinning behaviour in parallel-plate geometries; a slip layer seems to form between the plate and the material in such standard geometries.The link between parallel-plate results and data from vane geometries is not clear in the literature.The power-law viscosity model was used to fit the steady-shear results from parallel-plate geometry.The torquerotation rate results were also obtained from a vane geometry for CNF suspensions at three solids levels (2-4 wt%).A finite element method was used to solve the flow equations for calculating the torque applied on the solid surfaces in the vane geometry.The power-law model gave reasonable results for the prediction of torque.It was shown by shear rate distributions that the shearing layers of the fluid existed predominately at radial positions close to the vane radius and the viscosity value at this shear rate becomes important in determination of the torque.