Daoyin Liu

Understanding wet particle collisions involving droplets is essential for optimizing industrial processes. This study employs interface-resolved simulations combining the volume of fluid model, surface tension model, particle motion model, and overset grids to analyze particle–droplet interactions. Key phenomena investigated include particle motion, droplet spreading, successive particle collisions, and liquid bridge stretching. In symmetric systems, particle dynamics and droplet interactions show consistent patterns. The peak droplet spreading area increases with higher initial velocities and larger droplet sizes. Conversely, it decreases with greater liquid viscosity. Rotational velocity increases with higher collision velocity, lower viscosity, smaller droplet size, and is strongly influenced by collision angle, exhibiting trends similar to normal relative velocity. Increased initial collision velocity amplifies capillary and viscous forces, leading to greater energy dissipation. Force–displacement analysis confirms alignment between kinetic energy dissipation components and total energy loss. Moreover, larger droplets significantly enhance energy dissipation and reduce energy gain effects. Higher liquid viscosity further strengthens liquid bridge forces. These findings highlight the complex interactions involved in droplet-mediated particle collisions within multi-particle systems.

In industrial-scale powder storage facilities, abnormal stress distribution on silo walls can lead to severe safety accidents, including structural deformation and collapses. The powder weight distribution in three-dimensional flat-bottomed silos was studied from the force chain network rearrangement of the micro-mechanism to the wall stress distribution of the macro-behavior. The effects of particle size, silo diameter, and powder type were considered using the discrete element method. At a constant filling height-to-diameter ratio (Hfilling/D), increasing particle size slightly raises the bottom load-bearing percentage, while maintaining a constant filling height significantly increases this percentage as silo diameter increases. The size effect notably affects load-bearing distribution and pressure accumulation on the silo wall. The bottom effect weakens the sidewall load-bearing capacity near the bottom. The average particle–wall friction coefficient in static packing is lower than the predefined value, indicating insufficient wall friction mobilization. Shallow silos primarily support powder weight from the bottom. As Hfilling/D increases, strong force chains develop, enhancing force transmission and uniformity, while enhancing the sidewall load-bearing capacity.

In this study, the dynamic behaviors of non-Newtonian fluid droplets with shear-thinning properties eccentrically impacting hydrophobic particle surfaces are investigated through a combination of numerical simulations and experiments. The simulation integrates the dynamic contact angle and a non-Newtonian fluid power-law model within the volume of fluid model framework. The effects of apparent viscosity (η), impact velocity (v0), and dimensionless eccentricity parameter (B) on the dynamic behaviors of non-Newtonian droplets are analyzed. Furthermore, the study offers insight into the progression of pressure distribution, kinetic energy, and liquid viscosity across droplets during the entire impact process. An energy balance analysis, which includes kinetic energy, surface energy, potential energy, and viscous dissipation, is employed to elucidate the fundamental physical mechanisms that govern the dynamics of eccentric impacts of non-Newtonian droplets. Finally, a model (Recr D* = −95.7 + 11 450.6e−B/0.18) is proposed to predict the adhesion or detachment of shear-thinning droplets eccentrically impacting hydrophobic particle surfaces.

In this study, the dynamic behavior of shear-thinning droplets impacting on a hydrophobic spherical surface is numerically investigated using the volume of fluid method coupled with dynamic contact angle and a power-law model. The differences in dynamic behaviors between shear-thinning and Newtonian droplets are first studied. By analyzing the distribution of pressure and shear rate inside the droplet, it is found that the shear-thinning behavior of the droplets leads to an uneven distribution of apparent viscosity upon impact, which in turn prevents droplet rebound. The effects of various impacting conditions, such as apparent viscosity, impact velocity, surface tension and dynamic contact angle, on the spreading factor and liquid film thickness of shear-thinning droplets are investigated. According to the behaviors of droplets, the impacting process can be divided into three phases: (I) initial deformation, (II) inertia-dominated, and (III) viscosity-dominated phases. In order to reveal the physical mechanisms that prevent shear-thinning droplets from rebounding on the hydrophobic particle surface, the conversion of kinetic energy, viscous dissipation, surface energy, and potential energy during the three phases of the impact process is also analyzed in detail.