Particle-Laden Flows within Evolving Fluid-Driven Fracture

A fluid-driven fracture exhibits rapidly evolving geometry and high-shear flows that create a complex environment for particle transport. Understanding particle transport under these conditions is essential for subsurface processes, where particle-laden flows control mineral transport in natural fractures and proppant placement in hydraulic fracturing. Prior studies in static and idealized geometries cannot capture the effects of transient flows, evolving confinement, and tip-scale geometry that govern transport in propagating fractures. Here, we investigate particle transport in a dynamically evolving fluid-driven fracture in transparent, 3D-printed cylindrical PMMA models using high-speed imaging. Particle-laden Newtonian fluids are injected at high pressure to induce fracture and enable direct visualization of particle motion. Results show that particles initially follow the fluid front but increasingly lag due to size exclusion near the narrowing tip. In water-driven fractures, particles become trapped as the fracture aperture narrows, and flow vortices further disrupt transport by diverting particles from the flow in the radial direction. In contrast, in more viscous fluids, higher resistance suppresses vortex formation and helps maintain particle-fluid coupling. These results highlight the coupled influence of fluid properties, flow structure, and tip-scale geometry on particle transport in confined, time-evolving multiphase flows within porous and fractured media.