Determination of the shear and extensional rheology of bubbly liquids with a shear-thinning continuous phase
Determination of the shear and extensional rheology of bubbly liquids with a shear-thinning continuous phase
复制标题
用剪切稀化连续相测定起泡液体的剪切和拉伸流变学
作者：
M. Torres;B. Hallmark;D. Wilson
研究了气泡体积分数、ϕ和气泡大小对κ/ι杂化卡拉胶溶液和ϕ ≤ 为0.25时的起泡液体的流变性的影响。使用(1)行星混合(平均气泡尺寸90-130mμm)，(2)混合后通过对称注射器泵送(25-38μm)，以及(3)AS(2)但使用非对称注射器(12-20μm)，制备了三种不同的气泡尺寸分布。在半稀释区，研究了10和20微克/L的牙胶浓度。未充气的胶溶液是粘弹性的，可以很好地模拟为单模Giesekus流体。剪切和拉伸过程中的气泡流体行为也可以用单模Giesekus流体来模拟。气泡液体的吉塞克斯参数与非充气溶液的吉塞克斯参数之间存在单调递增的ϕ依赖关系。低剪切速率乳状液的表观粘度符合Choi和Schowalt(Phys流体18：420,1975)模型预测的趋势，而迁移率参数和松弛时间与ϕ呈线性关系。在这些测试中，气泡大小只显著影响灯丝的伸长，影响迁移率参数。需要进一步的工作来用微观机械模型来解释观察到的现象。
The effect of bubble volume fraction, ϕ, and bubble size on the rheology of rheology of κ/ι-hybrid carrageenan gum solutions and bubbly liquids with ϕ ≤ 0.25 was studied in steady shear using a parallel plate configuration and in extension using a filament stretching device. Three different bubble size distributions were prepared using (1) planetary mixing (mean bubble size 90–130 μm), (2) mixing followed by pumping through a symmetric syringe (25–38 μm), and (3) as (2) but using an asymmetric syringe (12–20 μm). Gum concentrations of 10 and 20 g/L, lying in the semi-dilute regime, were studied. The unaerated gum solutions are viscoelastic and could be modelled very well as a single-mode Giesekus fluid. The bubbly liquid behaviour in both shear and extension could also be modelled as a single-mode Giesekus fluid. The Giesekus parameters for the bubbly liquids were related to those of the unaerated solutions by monatonic increasing dependencies on ϕ. The low shear rate apparent viscosity followed the trend predicted by the Choi and Schowalter (Phys Fluids 18: 420, 1975) model for emulsions, while the mobility parameter and relaxation time were linearly dependent on ϕ. In these tests bubble size only affected filament extension noticeably, influencing the mobility parameter. Further work is required to explain the observations in terms of micromechanical models.