Study of the flow field in the magnetic rod interfacial stress rheometer.
Study of the flow field in the magnetic rod interfacial stress rheometer.
复制标题
磁棒界面应力流变仪流场研究。
作者：
T. Verwijlen;P. Moldenaers;H. Stone;J. Vermant
一些技术应用、消费品和生物系统从具有粘弹性界面流变特性的复杂流体界面的存在中获得它们的功能。这种界面的“过剩”流变特性的测量是复杂的，由体相和界面流的紧密耦合。在目前的工作中，界面流场的分析，数值模拟和实验结果的磁棒界面应力流变仪（ISR）。需要数学解决方案来校正实验确定的表观界面剪切模量和相位角由周围相施加的阻力，特别是在低Boussinesq数。从Navier-Stokes方程出发，采用广义Boussinesq-Scriven方程作为适当的边界条件，对问题进行了解析和数值求解。此外，界面流场的实验数据的报告，通过以下的示踪剂粒子的轨迹在界面上与时间。这三种方法之间存在良好的一致性，表明解析解和数值模拟都能充分描述流场和杆处的局部界面剪切速率。基于这些结果，提出了一种算法来校正ISR的实验数据，并进行了评估，该算法可以扩展到不同类型的界面剪切流变仪和几何形状。获得了更高的精度，并且ISR的测量范围向更小幅度的粘度和弹性模量扩展。
Several technological applications, consumer products, and biological systems derive their functioning from the presence of a complex fluid interface with viscoelastic interfacial rheological properties. Measurements of the "excess" rheological properties of such an interface are complicated by the intimate coupling of the bulk and interfacial flows. In the present work, analytical, numerical, and experimental results of the interfacial flow fields in a magnetic rod interfacial stress rheometer (ISR) are presented. Mathematical solutions are required to correct the experimentally determined apparent interfacial shear moduli and phase angles for the drag exerted by the surrounding phases, especially at low Boussinesq numbers. Starting from the Navier-Stokes equations and using the generalized Boussinesq-Scriven equation as a suitable boundary condition, the problem is solved both analytically and numerically. In addition, experimental data of the interfacial flow field are reported, obtained by following the trajectories of tracer particles at the interface with time. Good agreement is found between the three methods, indicating that both the analytical solution and the numerical simulations give an adequate description of the flow field and the resulting local interfacial shear rate at the rod. Based on these results, an algorithm to correct the experimental data of the ISR is proposed and evaluated, which can be extended to different types of interfacial shear rheometers and geometries. An increased accuracy is obtained and the measurement range of the ISR is expanded toward viscosities and elastic moduli of smaller magnitude.