Using an immersed boundary-lattice Boltzmann method, we investigated the response of dense granular suspensions to time-varying shear rates and flow reversals. The apparent viscosity and the evolution of particle clusters were analysed. The solids fractions and particle Reynolds numbers varied over the ranges 5% ≤ φv ≤ 47% and 0.11 ≤ Rep ≤ 0.32. The simulations included sub-grid scale corrections for unresolved lubrication forces. The contribution of the tangential lubrication corrections to the shear stress is dominant when φv surpasses 30%. For φv > 35%, increasing shear-thickening is seen with increasing φv. Following a shear reversal, the number of clusters temporarily increases and then decreases to a stable value over the same time scale as the development of the wall shear stress (and apparent viscosity). Simulations with several step changes in the shear rate show the effects of the previous shear history on the viscosity of the suspension.
A spatially resolved 1-D pressure filtration model was developed for a slurry of edible fat crystals. The model focuses on the expression step in which a cake is compressed to force the liquid through a filter cloth. The model describes the local oil flow in the shrinking cake modeled as a porous nonlinear elastic medium existing of two phases, viz. porous aggregates and inter-aggregate liquid. Conservation equations lead to a set of two differential equations (vs time and vs a material coordinate ) for two void ratios, which are solved numerically by exploiting a finite-difference scheme. A simulation with this model results in a spatially resolved cake composition and in the outflow velocity, both as a function of time, as well as the final solid fat contents of the cake. Simulation results for various filtration conditions are compared with experimental data collected in a pilot-plant scale filter press.