Particle-Scale Modeling of Water-Spray Dust Suppression in Underground Excavation: A Weighted DSMC Framework for Droplet–Dust Capture

Water spraying is widely used for dust suppression in underground excavation, but the particle-scale mechanisms governing droplet–dust collision and capture remain insufficiently understood. This study develops a weighted Direct Simulation Monte Carlo (DSMC) framework that tracks spray droplets and dust particles in a two-dimensional prescribed airflow field and models stochastic collision, capture, and agglomeration. The model reproduces the pressure-dependent macroscopic capture response observed experimentally, with relative deviations below 3% at water pressures of 6 MPa and above. Increasing water pressure improves atomization and spray penetration and increases the probability of droplet–dust collision. At higher water pressures, the increase in capture efficiency becomes smaller, and the water consumption continues to rise. A narrower droplet-size distribution increases the effective droplet number density and improves spatial matching with dust particles. Fine dust is more difficult to capture because its lower inertia enables it to follow airflow around droplets, whereas capture efficiency generally increases with particle size before stabilizing. Atomization and spray incidence angles primarily affect capture by altering the spray coverage, local droplet concentration, and collision distribution. The weighted DSMC framework provides a particle-scale approach for exploratory comparison of spray operating conditions and spray geometry under the prescribed model assumptions.