abstract

• We studied the terminal velocity of a packed array of bubbles, a bubble cluster, rising in different fluids: a Newtonian fluid, an elastic fluid with nearly constant viscosity (Boger fluid), and a viscoelastic fluid with a shear dependent viscosity, for small but finite Reynolds numbers (1 × 10-4 < Re < 4). In all three cases, the cluster velocity increased with the total volume, following the same trend as single bubbles. For the case of clusters in elastic fluids, interestingly, the so-called velocity discontinuity was not observed, unlike the single bubble case. In addition to the absence of jump velocity, the clusters did not show the typical teardrop shape of large bubbles in viscoelastic fluids and the strength of the negative wake is much weaker than the one observed behind single bubbles. Dimensional analysis of the volume-velocity plots allowed us to show that, while the equivalent diameter (obtained from the total cluster volume) is the appropriate length to determine buoyancy forces and characteristic shear rates, the individual bubble size is the appropriate scale to account for surface forces. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4874630].

authors

• Hernández-Cordero J.
• Lantenet J.
• Vélez Cordero Juan Rodrigo
• Zenit R.

publication date

• 2014-01-01

published in

• Physics of Fluids  Journal

keywords

• Newtonian liquids; Non Newtonian flow; Reynolds number; Shear flow; Velocity; Viscoelasticity; Viscosity; Dimensional analysis; Equivalent diameter; Finite Reynolds number; Newtonian fluids; Shear-dependent viscosity; Terminal velocity; Vis-coelastic fluids; Volume velocities; Non Newtonian liquids

Digital Object Identifier (DOI)

• 10.1063/1.4874630

start page

end page

volume

• 26

issue

• 5