Influences of wetting step surfaces on the maintenance of bubbles

The maintenance of bubbles is crucial for the efficiency of bubble drag reduction technology. Wetting step surfaces have the potential to improve the performance of bubble maintenance, which has not been fully researched. To study the bubble maintenance problems on wetting step surfaces, a numerical model is established to study the deformation and motion characteristics of bubbles on wetting step surfaces under incoming shear flow. The research analyzes the constraints and hysteresis effects of wetting step parameters on bubbles and investigates the fundamental conditions for maintaining bubbles with surface wetting properties. Compared with the cases on uniform wetting surfaces, bubbles on wetting step surfaces could resist much higher incoming flow speed. Increase of the wetting step value or contact angle of hydrophobic region leads to higher resistance of bubble to shear stress from the incoming flow. The influence of increasing the contact angle of the hydrophobic area is more pronounced on bubble maintenance than that of increasing wetting step value. Furthermore, small bubbles are beneficial to the maintenance of bubbles on wetting step surfaces. This research could provide a reference for the coupling design of wetting surface and bubble drag reduction technology in ocean engineering.