Characterization of Bubble Shapes in Non‐Newtonian Fluids by Parametric Equations

• Published in: Chemical engineering & technology Vol. 42; no. 11; pp. 2321 - 2330
• Main Authors: Xu, Feishi, Midoux, Noel, Li, Huai-Zhi, Hébrard, Gilles, Dietrich, Nicolas
• Format: Journal Article
• Language: English
• Published: Frankfurt Wiley Subscription Services, Inc 01.11.2019; Wiley-VCH Verlag
• Subjects: Air bubbles; Aspect ratio; Biotechnology; Bubble dynamics; Bubble shape; Bubbles; Computational fluid dynamics; Deborah number; Dimensionless numbers; Fluid flow; Gas‐liquid system; Hydrodynamics; Life Sciences; Mathematical models; Newtonian fluids; Non‐Newtonian fluid; Parameters; Parametric equations; Rheological properties; gas-liquid system; non-Newtonian fluid; bubble shape; bubble dynamics
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.201800690

Based on experiments with single air bubbles rising in stagnant non‐Newtonian fluids, an innovative model containing the aspect ratio (E) and two parameters (α, β) was proposed and proved to be capable of characterizing the bubble shape from spherical/ellipsoidal to prolate/oblate‐tear with good accuracy. Several impacts on bubble deformation were investigated, involving the rheological properties of the fluids and different forces exerted on the bubble, which were quantified by multiple dimensionless numbers (e.g., Reynolds, Eötvös, and Deborah number). Within a wide range, the empirical correlations were obtained for parameter β, and between α and β. Together with the shape model, a complete system was set up for bubble shape characterization and prediction that will provide new ideas for future studies on bubble hydrodynamics. Characterization of bubble shapes in non‐Newtonian fluids, from spherical/ellipsoidal to prolate/oblate‐tear, was achieved based both on experiments with single air bubbles rising in stagnant fluids and on a new model containing the aspect ratio and two parameters. The cusp of the bubbles is related to the viscoelasticity and the shear‐thinning level of the solutions.