Kostrzewa MM, Delgado A, Wierschem A (2016)
Publication Type: Journal article
Publication year: 2016
Publisher: Springer Verlag (Germany)
Pages Range: 16p
DOI: 10.1007/s00707-015-1472-6
The effect of concentration and molar ratio of cetyltrimethylammonium bromide with sodium salicylate (CTAB/NaSal) micellar aqueous solutions on the settling of non-Brownian spheres is determined. The micelles cause shear thinning, which may result in a shear-stress plateau. The measurements were performed in the wide range of Weissenberg numbers showing drag reduction and enhancement. Maximum drag coincides with the minimum relaxation time. For equimolar solutions, a correlation between Weissenberg number and normalized drag correction factor is proposed. The average settling velocity decreases proportionally to the inverse CTAB/NaSal concentration squared and is closely related to the micellar network size. Salt excess in 10 mM CTAB solutions results in an exponential increase in the average velocity. We find steady and unsteady regimes for the particle motion. In equimolar solutions, the frequency decreases with the concentration, whereas the dominant frequency does not change with salt excess, but is associated with the shear-stress oscillations. We show that the unsteady particle motion is related to the rheological time-dependent properties of the micellar solutions.
APA:
Kostrzewa, M.M., Delgado, A., & Wierschem, A. (2016). Particle settling in micellar solutions of varying concentration and salt content. Acta Mechanica, 16p. https://dx.doi.org/10.1007/s00707-015-1472-6
MLA:
Kostrzewa, Monika Maria, Antonio Delgado, and Andreas Wierschem. "Particle settling in micellar solutions of varying concentration and salt content." Acta Mechanica (2016): 16p.
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