BOUNCING BEHAVIORS OF A BUOYANCY-DRIVEN BUBBLE ON A HORIZONTAL SOLID WALL

It is not only interesting but also complex that buoyancy-driven bubbles rising in viscous liquids. In particular, the interactions between bubbles and boundaries (e.g., solid walls) is relevant in practical applications and these interactions may have a significant effect in the global behaviors of the multi-phase fluids. In this work, the rising, collision and bouncing to a horizontal solid wall for a single bubble are studied by axisymmetric computations. The incompressible, density-variable Navier-Stokes equations with surface tension are used to describe the gas-liquid flow and are solved by a tree-based finite volume method (FVM). The evolution of bubble shape is implemented by using a volume of fluid (VOF) approach that combines a balanced surface tension force calculation and a height-function curvature estimation. To finely resolve the local but fast topological evolutions of bubble, the technique of adaptive mesh refinement (AMR) is used. Starting with the basic phenomenon of bubble impacting and bouncing, we explore the effects of Galilei number Ga and approach velocity U_\rm a. To study the bubble behaviors under different conditions both qualitatively and quantitatively, the evolution of the velocity vector field and a lot of parameters such as bouncing height H, bouncing period T,rising velocity U, axial coordinate zand coefficient of restitution C_\rm r are analyzed. Based on the results, we find that the bubble bouncing behaviors are pretty sensitive to the Galilei number. The increase of Ga promotes the bouncing and signifies the deformation of bubbles, increasing the collisions of bubbles, bouncing parameters and the coefficient of restitution. However, the value of C_\rm ris nearly unaffected by the variation of the approach velocity, indicating that U_\rm ais not a governing parameter for the bubble bouncing motion.