Surface Remobilization of Gas Bubbles in Polymer Solutions Containing Surfactants

On the critical bubble volume at the rise velocity jump discontinuity in viscoelastic liquids

“…Therefore the appearance of a cusp at the rear stagnation point does not ensure the appearance of a velocity jump. This is consistent with the observations by Rodrigue and Blanchet [10].…”

“…The authors of [7] showed that data previously published by several authors also appear to correlate with a critical capillary number of order one. They noted further that the presence of a cusp is not a sufficient condition for the appearance of a discontinuity, which was confirmed, for instance, in the papers of De Kee et al [8,9], Rodrigue and Blanchet [10], and also in the present work, where despite a clearly visible cusp at the rear stagnation point in some cases no jump appeared. Extensive investigations on the rise velocity jump discontinuity of bubbles in polymer solutions can be found in [10][11][12][13][14][15], which represent the recent developments on this phenomenon.…”

“…The w = 0.1 wt.%, as well as the w = 0.3 wt.% solutions show a discontinuity in the velocity volume plot, though the transition does not appear as abrupt as in the case of the aqueous Praestol 2500 solutions. Rodrigue and Blanchet [10] obtained a similar transition behaviour by enhancing the concentration of a surfactant added to the polymer solution in order to eliminate the discontinuity (see Fig. 5 in [10]), which they did not identify as a jump any more.…”

“…It was already noted in the work of Rodrigue and Blanchet [10], and in Rodrigue et al [12], that care should be given to the possible effect of elongational viscosity of viscoelastic liquids for further investigations. As shown in the paper of Stelter et al [21], the transient elongational viscosity η E (t) is related to the relaxation time λ E according to the relation…”

“…The jump could be the result of the normal forces acting in the vicinity of the bubble, removing molecules from the bubble surface or causing a sudden change in the interfacial conditions. In the work of Rodrigue and Blanchet [10] it is shown that the jump can be eliminated by using surfactant concentrations above the critical association concentration (CAC). From their observations they concluded that the origin of the jump is most likely related to a change in interfacial conditions due to an imbalance in surface tension gradient and elastic forces at the gas-liquid interface.…”