Permeability of deforming soft particle packs

The permeability of the fluid between packs of particles is an important parameter for a range of natural and industrial applications. Here, we start from experiments in which soft spherical particles-"soft balls"-are compressed uniaxially, resulting in particle-particle flattening and an overall decrease in interstitial volume fraction ϕ down to very low values. During deformation, the soft particle packs were scanned in three dimensions using x-ray tomography; we segment these data to isolate the fraction between the particles. We then run lattice Boltzmann fluid flow simulations through the domains to determine the permeability. Additionally, we determine the specific surface area s and ϕ. Together, we use these parameters to test and validate a semiempirical extension to a theoretical percolation model, to propose a framework for predicting permeability in deforming soft particle systems. Once validated, we compare this model to the permeability of the fluid in packs of hard particles and during particle sintering; we conclude that this model is applicable to a wide range of initially particulate systems with all the geometric information encoded in s.