(533d) Fluid Flow Through Networks in the Collapse of Colloidal Gels

In unstable colloidal gels, the viscous flow through the non-neutrally buoyant colloidal network determines the initial rate of collapse[1]. The resistance to this flow through the network is characterized by the permeability.  The permeability is generally accepted to be a power-law function of volume fraction, where the power is dependent on the fractal dimension of the network.  To test this with direct numerical simulations, randomly generated diffusion-limited-cluster-aggregated networks of spheres and other particle are generated along with ordered lattices that span the containing structure or periodic cells.  These networks will be characterized using the fractal dimension by measuring the length of the network strands with different sized measurement scales[2].

The permeability is then determined using finite element solutions of the Navier-Stokes equations of pressure-driven flow of Newtonian fluids through the networks.  With this method, we calculate the permeability’s dependence on volume fraction, particle size and shape, and fractal dimension.  In addition, a comparison of periodic boundary conditions to networks in finite size containers is used to test the effect of particle pressure on the dynamics in these systems[3].