Numerical study of Taylor bubble dynamics across a vertical–inclined transition in stagnant liquid

This study focuses on understanding the 3D flow pattern of a Taylor bubble during the transition from a vertical to an inclined tube. Through Computational Fluid Dynamics (CFD) simulations, two cases are analyzed with distinct fluid properties, inducing different Eötvös and Morton numbers, allowing to explore how viscous and gravitational forces determine bubble shape, velocity, and stability of the flow. In case A, which represents a lower-viscosity system, the bubble undergoes significant deformation, with noticeable asymmetry and a recirculating wake developing at the bubble’s tail. The bubble rising velocity, as well as the bubble length, fluctuates significantly during the passage in the transition region. In contrast, case B, which has a higher viscosity, exhibits a more stable flow with less pronounced bubble deformation, resulting in a more constant bubble rising velocity and a more uniform bubble length throughout the transition region. These findings demonstrate the critical role of fluid properties in determining slug flow behavior in non-linear geometries.