Single bubble rising behaviors in Newtonian and non-Newtonian fluids with validation of empirical correlations: A computational fluid dynamics study

Abstract

The bubble rising (BR) dynamic is a common phenomenon in numerous processes of industries. Here, a single air BR behavior is studied using computational fluid dynamics (CFD) modelling in a Newtonian fluid (NF) and non-Newtonian fluid (nNF). The volume of fluid formulation with the continuum surface force equation is used to track the air bubble in a NF, while the viscosity of the nNF fluid is estimated by using the power-law equation. The bubble terminal velocity and its shape deformation, as well as the influence of different dimensionless numbers on BR characterization are investigated. The bubble rise in NF, the bubble terminal velocity increases with decreasing Morton number, and bubble moves up in a zigzag way with shape oscillation for the case of low Morton number of the NF. The bubble rise in nNF, the bubble terminal velocity increases with the increases in the rheological index, and bubble size as well as its shape transforms from an ellipsoidal to ellipsoidal cap types. It is found that the drag coefficient is high in a low rheological index compared with the high rheological index. The CFD results are compared with experimental results and empirical correlations reported in the literature. Good agreements are found between the CFD and the literature data for both fluids.