Modelling the dissolution of non-aqueous phase liquid blobs in sphere packings

Pore-scale modelling is appealing for investigating and obtaining macroscale constitutive equations for multiphase porous medium systems, because this approach bridges the macroscopic and microscopic scales. In this study, we develop a method to simulate and study the dissolution of non-aqueous phase liquid (NAPL) blobs; accurately quantifying NAPL mass transfer is crucial for modelling decontamination studies faithfully. We simulate a random packing of spheres and a residual NAPL distribution by matching macroscopic morphological descriptors of an experimental NAPL distribution; then we simulate single-phase flow by using a lattice-Boltzmann approach. Finally we numerically solve the advection-diffusion equation in the pore space to simulate mass transfer and transport of the dissolved components. Based upon different simulation results, we evaluate the sensitivity of the mass transfer coefficient with respect to two non-dimensional parameters and compare the simulation results to existing empirical relationships.