On the terminal velocity of single bubbles rising in non-Newtonian power-law liquids

A. Battistella, S.J.G. van Schijndel, M. W. Baltussen, I. Roghair (Corresponding author), M. van Sint Annaland

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

24 Citaten (Scopus)
223 Downloads (Pure)

Samenvatting

To describe bubbly flows, an accurate prediction of the bubble rise velocity is crucial. For non-Newtonian fluids, closures for the bubble rise velocity provided in the literature are usually empirical and rather restricted in their applicability. In this work, a Front-Tracking Computational Fluid Dynamics model has been used to investigate the behaviour of a single bubble rising in a power-law fluid, for a very wide range of viscosities covering both shear-thinning and shear-thickening behaviour, where the power-law exponent n was varied between 0.5 and 1.5 and for three different bubble diameters (viz. 0.5 mm, 2 mm and 4 mm). The non-Newtonian behaviour of the continuous phase strongly influences the shape of the single rising bubbles caused by the viscosity profiles that develop in the flow field. As a consequence, large non-spherical bubbles become more spherical in shear-thickening fluids (in comparison to the same bubble in a Newtonian liquid), whereas small spherical bubbles lose their sphericity in shear-thinning fluids. To determine the bubble rise velocity for bubbles in non-Newtonian fluids with a power law behaviour, the drag closure derived for bubbles rising in Newtonian liquids proposed by Dijkhuizen et al. (2010), which combines viscous drag and shape-induced drag in a single correlation, is adapted using a modified Reynolds number. In this work it is shown that this adapted correlation is able to predict the terminal rise velocity of single bubbles rising in non-Newtonian power-law fluids within 20% accuracy for the majority of the investigated cases, provided that the drag regime does not change.

Originele taal-2Engels
Artikelnummer104249
Aantal pagina's11
TijdschriftJournal of Non-Newtonian Fluid Mechanics
Volume278
DOI's
StatusGepubliceerd - apr. 2020

Financiering

This work is part of an Industrial Partnership Programme of the Foundation for Fundamental Research on Matter (FOM) which is part of the Dutch Research Council (NWO). This Industrial Partnership Programme is co-financed by Nouryon Chemicals International B.V., DSM Innovation Center B.V., Sabic Global Technologies B.V., Shell Global Solutions B.V., and Tata Steel Nederland Technology B.V.

FinanciersFinanciernummer
Tata Steel Europe Ltd.
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Foundation for Fundamental Research on Matter

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