Direct Flow Simulations of Thixotropic Liquids in Agitated Tanks

Yield-stress liquids often show time-dependent behaviour (thixotropy): the network providing the yield stress in the liquid needs time to build up after being destroyed by liquid deformation. In numerical simulations of thixotropic liquids the network's integrity can be accounted for by solving a scalar transport equation in a network structure parameter, and relating that structure parameter to the apparent viscosity. We apply this method for simulating the laminar and transitional flow in a baffled mixing tank equipped with a Rushton turbine with emphasis on the start-up of the flow from a stagnant situation, and on comparing liquids with time dependent and time independent rheology.