Simulations of complex flow of thixotropic liquids

A procedure for detailed simulations of flow of purely viscous thixotropic liquids is outlined. The local viscosity of the liquid relates to the level of integrity of a network in the liquid. The time-dependence of the liquid's rheology is due to the finite rate with which the network in the liquid builds up or breaks down, the latter due to fluid deformation. This concept has been incorporated in a lattice-Boltzmann discretization of the flow equations coupled to a scalar transport solver with the scalar representing the network integrity. It results in a computationally efficient algorithm that allows for very detailed (three-dimensional and time-dependent) simulations of thixotropic liquid flow in complexly shaped confinements. After verifying the numerical procedure by means of a few benchmark cases, it is applied to study the influence of the Deborah number on the transient behavior as well as the quasi steady-state flow in a mixing tank equipped with a Rushton turbine.