Flow in the negative wake of a Taylor bubble rising in viscoelastic carboxymethylcellulose solutions: particle image velocimetry measurements

• Type: Article in International Scientific Journal
• Date: 2004

Authors

Renato G. Sousa (Author) Other; S. Nogueira (Author) Other; Alexandra Rodrigues Pinto (Author) FEUP; M. L. Riethmuller (Author) Other; João Bernardo de Campos (Author) FEUP

Journal

Title: Journal of Fluid Mechanics

Vol. 511

Pages: 217-236

ISSN: 0022-1120

Publisher: Cambridge University Press

Indexing

ISI Web of Knowledge - 15 Citations

Scopus - 18 Citations

Scientific classification

FOS: Engineering and technology > Mechanical engineering

CORDIS: Technological sciences > Technology ; Technological sciences

Other information

Authenticus ID: P-000-9D6

DOI: 10.1017/s0022112004009644

Abstract (EN): A simultaneous technique employing particle image velocimetry (PIV) and shadow-graphy was used to study vertical slug flow in non-Newtonian fluids. Two aqueous solutions of 0.8 and 1.0wt% carboxymethylcellulose (CMC) were studied and the flow field around individual Taylor bubbles fully characterized. The rheological fluid properties and pipe dimension yielded Reynolds numbers of 8 and 4 and Deborah numbers of 0.2 and 0.4. A negative wake was found downstream of the Taylor bubbles in both fluids. Below the bubble trailing edge, along the axis region, the fluid flows in the opposite direction to the bubble (negative wake), originating rotational liquid movements in adjacent regions. Even far downward from the bubble, rotational liquid movements are clearly seen and measured. In the 1.0wt% CMC solution, the bubble trailing edge has the shape of a two-dimensional cusp. This two-dimensional cusp, of small dimensions, is seen in different orientations during the bubble rise-indicating a fast rotational movement. The asymmetrical shape of the trailing edge is responsible for small asymmetries in the flow in the wake region (three-dimensional flow). The asymmetrical shape associated with the rotational movement is responsible for an unsteady flow of small amplitude. In the 0.8 wt% CMC solution, the shape of the trailing edge changes during the bubble rise. An axisymmetric axial oscillation a continuous expansion and contraction of the trailing edge, is the origin of this behaviour. This oscillatory movement is responsible for an unsteady flow of small amplitude in the wake region.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 20