The objective of this report is to study a model of agravity and shear induced consolidation process of a dense,flocculated suspension.
The suspension is modeled as a two-constituent mixture of afluid and solid particles by an Eulerian two-phase fluid model.Both phases are described as incompressible continuous mediacoupled through an interaction force between the phases.
Constitutive relations for the stresses and the interactionforces in the mixture are fitted to experimental data. Theshear-thinning is modeled by a non-constant viscosity thatdepends on the volume fraction of particles and on the shearrate of the flow. Since the concentration of particles in themixture is high, irreversible inter-particle forces are alsoincluded in the model.
A numerical solver for one and two dimensional problems isdesigned using finite difference methods both in time andspace. To investigate the in fluence of shear and viscosity onthe process a number of simulations are performed.
In the 1Dca se, the suspension is confined in a closed boxand consolidates due to a constant gravity field directedtoward the bottom. Conclusions from mathematical analysis areverified by calculations and shows that the size of theviscosity is important for the time scale of the problem. Wealso show that our results in 1Dare consistent with other workdone on this subject.
To study the in fluence of shear and viscosity on theconsolidation speed 2Dsim ulations are performed. Shear isinduced on the suspension by a movement of the bottom wall witha constant speed. Experiments show that the movement does influence the consolidation rate but the observed differences inthe numerical experiments were small.
Stockholm: Numerisk analys och datalogi , 1999. , vi, 60 p.