Particle transport regime transitions in fractured media under gas–liquid two-phase flow
Abstract
Particle transport in confined channel flows under gas–liquid two-phase conditions is governed by the interplay among fluid drag, particle inertia, wall shear stress, and turbulent fluctuations. This study investigates the transport regime transitions of particulate solids in planar fracture channels through combined transparent-fracture visualization experiments and Euler–Lagrange gas–liquid two-phase flow and particle-tracking numerical simulations. The experiments cover gas flow rates of 3–10 l/min, liquid flow rates of 10–100 l/h, and particle diameters of 50–200 μm. Two image-derived indicators are introduced: front migration distance Lm for along-channel travel capacity and suspension area fraction As/A0 for the extent of particle detachment from the deposited bed. Dimensionless power-law relationships are established (Lm/L∝ReG0.51ReL0.17; As/A0 ∝ ReG0.23ReL1.94), showing that gas-phase flow intensity primarily governs normalized streamwise migration, whereas liquid-phase flow intensity mainly controls the suspension extent. Four transport regimes are identified (I: bottom deposition and local disturbance; II: wall slip and along-channel migration; III: recirculation entrainment with local suspension; IV: large-scale suspended transport), with an additional III–IV transitional zone. Numerical simulations reveal the differentiated flow-structure control mechanisms: increasing the liquid flow rate primarily enhances wall shear stress, promoting near-wall particle mobilization; increasing the gas flow rate primarily elevates turbulent kinetic energy, strengthening entrainment and streamwise transport. Fine particles more readily enter the suspended regime due to weaker inertia, whereas coarse particles are dominated by gravity and tend to settle. These findings provide a mechanistic framework for understanding how wall shear stress and turbulent kinetic energy jointly control particle entrainment, migration, and suspension in confined multiphase channel flows.