Rise of a confined bubble in a wedge channel under different gravity

The migration of gas bubbles in confined geometries is of fundamental interest in both terrestrial and space-based fluid systems. This study investigates the rising dynamics of a gas bubble in a wedge-shaped channel under varying gravity conditions. Three-dimensional numerical simulations are performed using the Volume-of-Fluid (VOF) method to resolve the bubble interface and the embedded-boundary method to represent the wedge channel walls. An artificial repulsive van der Waals force is introduced to maintain a sub-grid thin film between the bubble and the wedge wall, enabling physically consistent interface dynamics without excessive mesh refinement. Parametric studies are conducted by varying gravity, liquid viscosity, and bubble volume. The bubble is initially spherical and not confined by the wedge walls. Under the action of gravity, the bubble accelerates toward the wedge vertex. When the bubble becomes confined by the walls, the curvature difference between the bubble’s top and bottom induces a capillary force that opposes gravity, causing the bubble to slow down. Eventually, the bubble reaches an equilibrium state, where its velocity becomes zero. A theoretical model is developed to predict the bubble’s equilibrium shape and position. The model and simulation results are in good agreement. The bubble deforms as it rises toward the equilibrium position. The bubble’s shape and rising velocity experience oscillations early on when the liquid viscosity is low and the bubble volume is large, particularly in the inertial-capillary regime. In contrast, for high viscosity and bubbles in the viscous-capillary regime, the evolution of bubble velocity is monotonic, but the bubble width can overshoot the equilibrium value and exhibit a higher chance of breaking. The findings in this study lay a foundation for future studies on capillarity-driven bubble migration under microgravity in ISS experiments.