Surface-wettability-induced sliding bubble dynamics and its effects on convective heat transfer

To explore the effects of wettability on heat transfer in sliding bubble dynamics, we investigated how the dynamics of sliding bubbles and heat transfer over a heated surface depend on the degree of wettability. We used volume-of-fluid scheme to track the interface of the dispersed phase via the local volume fraction. The results of the numerical model used in this study were consistent with those of experimental studies. After bubble collision, the bubble was found to adhere to a heated hydrophobic surface, as the bubble impinged upon the surface. The heat-transfer coefficient increased significantly in the region of the hydrophobic surface where the adhered bubble passed. The bubble completely adhered to the surface, as the adhesion force continuously increased. When the contact angle increased in the surface-contact regime (above 110°), the bubble spread out over the surface. The average Nusselt number in the surface-contact regime was found to be greater than that in other regimes (below 110°); thus, the surface more strongly affected heat transfer.