Numerical simulation of single bubble motion along inclined walls: A comprehensive map of outcomes

Abstract

The bubble interactions with a wall affect many industrial application's performance. The single bubble rising in a stagnant fluid is studied next to an inclined wall. The two phases are incompressible, and the interface between phases is captured with the volume of fluid (VoF) method. The influence of various parameters such as wall slope (θ), contact angle (φ), and dimensionless numbers (Morton and Bond) on the bubble-wall regime is investigated. The numerical results (bubble shape and terminal velocity) are validated with experiments.After comprehensive numerical simulation over a wide range of Bond (1≤Bo≤40) and Morton (2.54×10−11≤Mo≤1×100) for inclined walls (0∘<θ<90∘), three bubble-wall interaction regimes: sliding, intermittent and non-contact are proposed and a regime map is plotted. We recognized two sliding regimes based on Bond numbers at small inclined walls (θ≤30∘). In the sticking sliding regime (Bo≤5), bubbles remain attached to the inclined wall. They make the wall dry along their path. But at higher Bond in film sliding, bubbles slip over a thin liquid film. Thus, the wall surface is always wet. The film thickness is linearly proportional to bubble diameter. Non-contact regimes occur at steep walls (θ≥70∘), where the bubble never touches the wall. In moderate wall slopes (30∘<θ<70∘), a bubble repeatedly impacts on and rebounds from the wall. The intermittent regime is an unstable regime, and it alters to a sliding or a non-contact regime based on Bond and Morton numbers.