The head-on collision between droplet and stationary particle under mesoscopic scale: Effect of sample size, velocity, viscosity, and wettability

Understanding the collision dynamics between a water mist droplet and a dust particle is crucial for uncovering the mechanisms of water mist dust suppression. However, studies involving mesoscopic-scaled samples have been rarely explored in the past. To address this gap, we performed numerical simulations and experiments to investigate collisions using realistic sizes of water mist and dust particles. Based on our findings, we proposed collision outcome regime maps to illustrate the different collision outcomes. These outcomes were categorized into four distinct regimes: rebounding, complete coalescence, ligament ripping, and skirt splashing. We have proposed both physical equations and fitting equations to describe the thresholds for rebounding, ripping, and splashing. Wettability was found to have a significant impact on the regime boundary equations, while the effects of sample size, collision velocity, and viscosity were minimal. Within the skirt splashing regime, we have proposed a power function to predict the residual liquid fraction of a collision based solely on the Reynolds number, and we have introduced a function combining the Weber number and the Ohnesorge number to predict the non-dimensional momentum transfer. By integrating the equations governing regime boundary, residual liquid fraction, and dimensionless momentum transfer, we can elucidate the dust suppression mechanism of water mist and offer optimized parameters for its effective use in mitigating dust. Interestingly, the study suggests that increasing droplet viscosity holds promise for enhancing dust suppression, rather than solely focusing on improving wettability. This introduces a new perspective to the development of additives for dust suppression.