Rheology of colloidal gas aphrons (microfoams) made from different surfactants

Abstract

This paper extends our previous study on microfoam rheology made from non-ionic (Tween 20) surfactants to ionic surfactants. Anionic (sodium dodecyl sulfate) and cationic (cetyl trimethylammonium bromide) surfactants were used to generate microfoams by stirring an aqueous surfactant solution at high speed in a baffled beaker. Pipe flow experiments were performed in cylindrical stainless steel pipe 1.5 mm in diameter under adiabatic and fully developed laminar flow conditions. The porosity φ, bubble size distribution, Sauter mean radius 32 r , surface tension σ, and pH are reported for each solution. The porosity varied between 0.54 and 0.72 while the Sauter mean radius ranged from 28 to 48 microns. Zero slip velocity was assumed to prevail at the foam-wall interface as previously observed and reported in the literature for stainless steel pipes. Volume equalized method was used to analyze the data obtained from pipe flow viscometer. In all cases, microfoams behave as a shear thinning fluid. The results suggest that the dimensionless wall shear stress where τ w is the wall shear stress, a γ & is the shear rate, σ is the surface tension, µ l is the liquid velocity, and ε = 1/(1-φ) is the specific expansion ratio. The average value of the power-law index m was found to be 0.64 ± 0.04 with 95% confidence interval.

Development of a Model Foamy Viscous Fluid

“…For these, the wall shear stress consists of a yield stress and a viscous component, while it can be considered that only the second one is observed in foamy fluids. It is commonly admitted in the literature on wet foams that the viscous component scales with Ca 2/3 for mobile interfaces but with Ca 1/2 for immobile interfaces that correspond to protein-covered bubble interfaces (Zhao et al, 2009;Politova et al, 2012). The good agreement between foamy fluids and wet foams seems intuitive, as phenomena are similar, especially close to the very wet limit, although the assumptions leading to s $ Ca 1/2 in wet foams are not valid for foamy fluids.…”

Toward the Effects of the Geometric and Operating Parameters on Colloidal Gas Aphron Stability

“…[14] Rheological properties of CGAs have also been investigated by several researchers. [15][16][17] The stability of CGAs is a critical property for the above-mentioned applications. [18] The high stability of CGA dispersion shows its ability to resist changes in bubble size and liquid content.…”

Experimental study of rheological properties of aphron based drilling Fluids and their effects on formation damage

“…About 100-300 bubbles were counted for each sample. Zhao et al [45] measured 130 to 240 individual bubbles using image analysis software and a microscope. Spinelli et al [30] used a similar microscope and image analysis software combination to work on the size distribution.…”