STUDY ON WALL DEPOSITION OF PARTICLES DURING GAS−SUSPENSION DISPLACEMENT

Particle deposition in gas−liquid−particle multiphase flow is of great significance for applications including clogging control, contamination remediation, material surface modification. In order to explore the mechanism of particle deposition, we set up a visualization experimental system of multiphase flow, and carried out gas−suspension displacement experiments in the Hele-Shaw cell under different controlling conditions of flow rates, gaps and particle sizes. A deposition coefficient is defined to quantitatively evaluate the particle deposition. It is found that different particle deposition patterns emerge during the displacement process. Building on the experimental findings, a particle deposition criterion, which takes the capillary number and the ratio of gap to particle size as control parameters, is proposed based on the liquid film theory and the flow field analysis at the gas−liquid interface. The criterion is compared and verified against the experimental results. The results show that there are three particle deposition patterns during the gas−suspension displacement process: no deposition, cluster deposition and uniform deposition, which are influenced by the flow rate, gap and particle size. As the flow rate and gap increase or the particle size decreases, the particle deposition pattern transitions from no deposition to cluster deposition and uniform deposition, and the particle deposition coefficient shows a trend of first rapid increase from zero, followed by stabilization. The residual liquid film on the wall is a necessary condition for the occurrence of the particle deposition. The critical geometric condition for the particle cluster deposition is the liquid film thickness at the interface stagnation point equal to the particle radius, and that for the particle uniform deposition is the liquid film thickness at the interface stagnation point equal to twice the particle radius. The proposed criterion accurately predicts the occurrence of particle deposition and the transition of deposition patterns, elucidating the controlling mechanism of particle deposition by the hydrodynamic condition and the ratio of gap to particle size.