Visualizing the Role of Particle Shape on 2D Inter-Particle Fluid Flow Using a Transparent Soil Surrogate

Many geotechnical applications benefit from advanced analysis of flow through porous media, such as filter and drain design, internal erosion and piping, and liquefaction, among others. In this study, a novel method is presented to visualize key components of fluid flow through pores of a saturated synthetic transparent granular media representing natural sand. Images of sand particles were captured using a dynamic image analyzer. 3D printing was then used to produce 2D extruded scaled models of representative particles that were used as casts to produce transparent extruded particles made of polyacrylamide hydrogel. Planar (i.e., plane strain) models having controlled porosity were prepared. Steady-state flow was established through the soil model, from which high-resolution images were captured. Image analysis methods were then used to visualize the flow field in the interstitial fluid. In order to capture the fluid flow, the pore fluid was seeded with highly reflective silver-coated hollow micro-spheres. A laser light source was used to illuminate a plane within the model. Particle image velocimetry (PIV) was employed for visualizing inter-particle fluid flow fields. The method allowed for investigating soil-fluid interactions of scaled hydrogel Ottawa sand and angular sand.