Mohammadigoushki Hadi, Dalili Alireza, Zhou Lin, Cook Pamela
Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL 32310, USA.
Department of Mathematics, New York City College of Technology, Brooklyn, NY 11201, USA.
Soft Matter. 2019 Jul 10;15(27):5483-5494. doi: 10.1039/c9sm00816k.
In this paper we investigate the flow of a shear banding wormlike micellar fluid based on cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal). The flow is studied in a custom-built Taylor-Couette (TC) cell via a combination of particle tracking velocimetry and in situ rheology. The spatiotemporal evolution of the velocity profile across the rheometer gap is tracked after an imposed step in the shear rate. In a range of shear rates the mixture shows shear banding behavior, that is distinct and differing shear rate profiles across the gap. As the shear bands form temporally, an elastic recoil including negative velocity (that is in the opposite direction to that of the imposed motion) is observed in a subset of the gap. While elastic recoil has been reported in experiments on monodisperse polymers [S. Ravindranath, et al., Macromolecules, 2008, 41, 2663-2670], on a wormlike micellar solution in a cone-plate rheometer [P. E. Boukany and S. Q. Wang, Macromolecules, 2008, 41(4), 1455-1464], and in theoretical studies [L. Zhou, et al., J. Non-Newtonian Fluid Mech., 2014, 211, 70-83; J. M. Adams, et al., J. Rheol., 2011, 55, 1007-1032] of wormlike micellar flows, it has not been previously reported in experiments on shear banding wormlike micelles in Taylor-Couette flows. Additionally, the mixture shows significant wall slip at the outer (stationary) Couette cylinder at high shear rates. Experimental results are compared to simulations of models of wormlike micelles, particularly the VCM model [L. Zhou, et al., J. Non-Newtonian Fluid Mech., 2014, 211, 70-83]. There are differences between the experimental results for this fluid and those reported previously. The difference arises from the size of the elasticity number which for the fluid reported in the paper is four orders of magnitude larger than that of other preparations.
在本文中，我们研究了基于十六烷基三甲基溴化铵（CTAB）和水杨酸钠（NaSal）的剪切带化蠕虫状胶束流体的流动。通过粒子跟踪测速法和原位流变学相结合的方式，在定制的泰勒-库埃特（TC）细胞中研究了该流动。在施加剪切速率阶跃后，跟踪流变仪间隙内速度分布的时空演化。在一定范围的剪切速率下，该混合物表现出剪切带化行为，即在间隙内有明显且不同的剪切速率分布。随着剪切带随时间形成，在间隙的一部分中观察到包括负速度（即与施加运动方向相反）的弹性回弹。虽然在单分散聚合物的实验中[S. Ravindranath等人，《大分子》，2008年，41卷，2663 - 2670页]、在锥板流变仪中的蠕虫状胶束溶液实验中[P. E. Boukany和S. Q. Wang，《大分子》，2008年，41(4)卷，1455 - 1464页]以及蠕虫状胶束流动的理论研究中[L. Zhou等人，《非牛顿流体力学杂志》，2014年，211卷，70 - 83页；J. M. Adams等人，《流变学杂志》，2011年，55卷，1007 - 1032页]都报道过弹性回弹，但此前在泰勒-库埃特流动中剪切带化蠕虫状胶束的实验中尚未报道过。此外，该混合物在高剪切速率下在外（固定）库埃特圆柱处表现出显著的壁面滑移。将实验结果与蠕虫状胶束模型的模拟结果进行了比较，特别是VCM模型[L. Zhou等人，《非牛顿流体力学杂志》，2014年，211卷，70 - 83页]。该流体的实验结果与先前报道的结果存在差异。这种差异源于弹性数的大小，本文所报道流体的弹性数比其他制剂的弹性数大四个数量级。
