Abstract

Objective Liquid bridges between wet particles are commonly found in industrial processes such as chemical engineering， energy production， food processing， and pharmaceutical manufacturing. The formation mechanism of these bridges plays an important role in optimizing processes such as fluidized bed granulation and the liquefaction of mineral soil particles. It affects particle uniformity， particle migration， and alters the distribution of pore structures. Therefore， this study aims to comprehensively investigate the dynamic evolution of liquid bridges and the liquid transfer mechanism during wet particle collisions.

Methods Through a combination of experiments and numerical simulations，the study investigated the effects of three factors，i.e.，dimensionless liquid film thickness， dimensionless initial particle spacing， and liquid viscosity， on the variations in dimensionless liquid bridge volume during liquid bridge formation between spherical particles. Synchronous and counter-rotation of stepper motors were used to rotate stainless steel balls， enabling uniform coating with dimethyl silicone oil and ensuring coating stability. The contours of experimental images before and after coating were extracted and compared to ensure both the coating thickness accuracy and uniformity of the liquid film. Three-dimensional numerical simulations based on the volume of fluid （VOF） method were conducted under conditions consistent with the experiments. Trend curves of dimensionless liquid bridge volume over dimensionless time were plotted to compare and validate the experimental and numerical simulation results， confirming the reliability of the research scheme.

Results and Discussion The results indicated that increasing liquid film thickness significantly enhanced the growth of the liquid bridge volume， including both the growth rate and the maximum volume. Specifically， for every 0.1 increase in the dimensionless liquid film thickness， the dimensionless maximum liquid bridge volume increased by approximately 0.02. The liquid bridge tended to saturate once the liquid film thickness exceeded a critical limit. When the initial particle spacing was 0.067， the maximum liquid bridge volume in the concave bridge state was observed at a film thickness of 0.22. Further increases in film thickness led to a morphological transition of the bridge shape from concave to convex.Increasing the initial particle spacing inhibited liquid bridge formation， reducing both the growth rate and the maximum volume. In experiments with constant film thickness， increasing the initial particle spacing from 0.067 to 0.133 resulted in an approximate 3.0% reduction in maximum liquid bridge volume， while an increase from 0.067 to 0.200 resulted in a reduction of approximately 4.9%. In numerical simulations， the corresponding decreases were about 2.6% and 3.9%， respectively.Within a dynamic viscosity range of 0.97 Pa·s to 9.74 Pa·s， variations in viscosity had little impact on the growth of the liquid bridge volume. This limited effect was attributed to the slow liquid flow during the formation of the liquid bridge. The capillary force reached a maximum velocity of less than 1 m/s and decreased continuously over time， indicating that capillary forces， rather than the viscous forces， dominated the evolution of the liquid bridge. Overall， the results demonstrated that liquid film thickness and initial particles pacing were key parameters controlling liquid bridge formation， while the influence of viscosity was limited under specific conditions.

Conclusion and Prospects This study systematically reveals the mechanisms by which various parameters influence the variation inliquid bridge volume during bridge formation. These findings provide theoretical guidance for optimizing particle bonding and agglomeration in industrial processes and for understanding liquid transport mechanisms between mineral soil particles. Additionally， a foundational model for dynamic studies of liquid bridges under complex working conditions was established in this study.Gravity has long been recognized as an important factor influencing experimental results in liquid bridge studies. Comparison and verification of experimental and numerical simulation results in this paper confirm that gravitational effects can be neglected using this research setup， providing experimental support for further investigations.In practical industrial processes such as powder handling， coal screening， and fluidized bed granulation， particles move relative to each other， and liquid bridges continuously form and rupture. Current research primarily focuses on liquid bridges formed by localized liquid between partially wetted particles. However， in practical applications， with the increased liquid content，liquid bridges can form between fully wetted particles. Future studies may investigate the effects of factors such as relative collision velocity and temperature variation on liquid bridge formation，explore dynamics of three-particle bridge systems， and examine both the rupture distance of liquid bridges between fully coated spherical particles and the liquid distribution patterns after rupture.

Keywords： wet particle； liquid bridge； liquid transfer； liquid volume method； numerical simulation

Get Citation:PAN Jiuqiang， WU Mingqiu. Experiments and direct numerical simulations on formation process of liquid bridges between spherical particles［J］. China Powder Science and Technology， 2026， 32（3）： 1-15.

Received: 2025-04-11 .Revised: 2025-06-30,Online: 2025-11-11.

Funding： The research was supported by the National Natural Science Foundation of China （Grant No. 22168014） and the Natural Science Foundation of Guangxi Province（Grant No. 2023GXNSFAA026480）.

DOI：10.13732/j.issn.1008-5548.2026.03.013

CLC No:O359+.1；TB4                   Type Code: A

Serial No:1008-5548（2026）03-0001-15