Numerical simulation of polydisperse dense particles transport in a random-orientated fracture with spatially variable apertures

Numerical experiments are conducted to quantify the transport behaviour of polydisperse dense particles through a randomly orientated fracture with spatially variable apertures. To be specific, fracture apertures are created by implementing the geostatistical algorithm of random field generation, while, based on the classical Local Cubic Law (LCL), pressure distribution and velocity field across the fracture are determined under given boundary conditions. Subsequently, the existing constant-spatial-step particle-tracking equations are modified by incorporating both particle settling gravity and fracture orientation to simulate particle transport behaviour. Using literature data, the simulation model in this study has been well validated. By simulating a set of well-designed scenarios, effects of fracture orientations, particle size-distribution, and aperture field heterogeneity and anisotropy on particle transport are systematically examined, while sensitivity analysis of the transport behaviour has been evaluated and compared. Compared to particle number breakthrough, mass breakthrough efficiency of particle plume is found to be usually much lower only except for the vertical orientation of a fracture. An increased inclination either parallel or perpendicular to the overall flow direction leads to an earlier particle breakthrough with a shorter tail on the breakthrough curves. A more heterogeneous fracture results in an enhanced longitudinal spreading of particle plume with distinct non-uniform fore- and back-end distribution. For a larger deviated particle size-distribution, particle plume during transport is evolved with more particles at its two-ends. In addition, it is observed from a vertical fracture that aperture anisotropy orientated parallel to the flow direction significantly enhances particle transport and spreading than that perpendicular to the flow direction. Fracture inclinations parallel and perpendicular to the flow direction yield a similar sensitivity on particle transport, while, compared to the heterogeneity of particle size-distribution, the aperture field heterogeneity affects particle transport more significantly. Comparing the aperture field consisting of a larger transverse correlation length with that of a larger longitudinal correlation length, the former is found with a more sensitive dependence of particle transport behaviour on aperture field anisotropy.

Automated summary

Numerical experiments were conducted to study the transport behavior of polydisperse dense particles through a randomly oriented fracture with spatially variable apertures. The study found that factors such as fracture orientation, particle size distribution, aperture field heterogeneity and anisotropy significantly influence particle transport behavior.