Reyes J Adrián, Corella-Madueño A, Mendoza Carlos I
Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364 01000, México D. F., Mexico.
J Chem Phys. 2008 Aug 28;129(8):084710. doi: 10.1063/1.2971043.
We consider a homogeneously aligned nematic liquid crystal confined in the region between two rotating coaxial cylinders. We study the nematic's director and velocity profiles induced by the imposed Couette flow and an applied radial electric field. We present calculations for the specific flow-aligning nematic liquid crystal 4(')-n-pentyl-4-cyanobiphenyl and numerically solve a hydrodynamic model assuming hard anchoring and nonslip boundary conditions. We calculate a phase diagram in the parameter space showing a region where there exist multiple equilibrium solutions for the nematic's configuration and a region where there exists only one stationary solution. We also study the rheology of the system by calculating the apparent viscosity and the first normal stress difference. We find that the competition between the Couette flow and the electric field gives rise to an interesting non-Newtonian response which switches its behavior from shear thickening to shear thinning by exceeding a critical field.
我们考虑一种均匀排列的向列型液晶，其被限制在两个旋转同轴圆柱之间的区域。我们研究由外加的库埃特流和径向电场引起的向列型液晶的指向矢和速度分布。我们给出了特定的流动取向向列型液晶4('-正戊基-4-氰基联苯)的计算结果，并在假设硬锚定和无滑移边界条件下对一个流体动力学模型进行了数值求解。我们计算了参数空间中的相图，该相图显示了一个区域，其中向列型液晶的构型存在多个平衡解，以及一个仅存在一个定常解的区域。我们还通过计算表观粘度和第一法向应力差来研究该系统的流变学。我们发现，库埃特流和电场之间的竞争产生了一种有趣的非牛顿响应，当超过临界场时，其行为从剪切增稠转变为剪切变稀。
