Effects of Non-Newtonian Viscosity and Suspended Particles on Torque Measurements in Rotational Viscometry

Accurate rheological characterization of fluids is of critical importance in a range of applications. A challenge associated with viscometric flows of non-Newtonian fluids is that both the shear rate and the shear stress will normally depend on the unknown viscosity of the fluid. A further complication arises when physical properties of the fluid, such as the spatial distribution of particles in particle-laden fluids, change over the course of the measurement. To gain insight into the flow of non-Newtonian fluids and particle suspensions in viscometric geometries, and how the fluid viscosity and neutrally buoyant particles affect the measurement, we solve the Navier-Stokes equation for a three-dimensional Couette geometry using the lattice Boltzmann method. With the model, secondary flows is observed at higher velocities, without major contributions in the torque measurement. When the particles are added, a large impact in the shear-rate field is noticed.