Patlazhan Stanislav, Vagner Sergei
Semenov Institute of Chemical Physics of the Russian Academy of Sciences, 4 Kosygin Street, Moscow 119991, Russia.
Institute of Problems of Chemical Physics of the Russian Academy of Sciences, 1 Semenov Avenue, Chernogolovka, Moscow Region 142432, Russia.
Phys Rev E. 2017 Jul;96(1-1):013104. doi: 10.1103/PhysRevE.96.013104. Epub 2017 Jul 10.
The peculiarities of simple shear flow of shear thinning fluids over a superhydrophobic wall consisting of a set of parallel gas-filled grooves and solid stripes (domains with slip and stick boundary conditions) are studied numerically. The Carreau-Yasuda model is used to provide further insight into the problem of the slip behavior of non-Newtonian fluids having a decreasing viscosity with a shear rate increase. This feature is demonstrated to cause a nonlinear velocity profile leading to the apparent slip. The corresponding transverse and longitudinal apparent slip lengths of a striped texture are found to be noticeably larger than the respective effective slip lengths of Newtonian liquids in microchannels of various thicknesses and surface fractions of the slip domains. The viscosity distribution of the shear thinning fluid over the superhydrophobic wall is carefully investigated to describe the mechanism of the apparent slip. Nonmonotonic behavior of the apparent slip length as a function of the applied shear rate is revealed. This important property of shear thinning fluids is considered to be sensitive to the steepness of the viscosity flow curve, thus providing a way to decrease considerably the flow resistance in microchannels.
数值研究了剪切变稀流体在由一组平行的充气凹槽和固体条纹组成的超疏水壁（具有滑移和黏附边界条件的区域）上的简单剪切流动特性。采用卡罗厄-亚苏达模型进一步深入研究了黏度随剪切速率增加而降低的非牛顿流体的滑移行为问题。结果表明，这一特性会导致非线性速度分布，进而产生表观滑移。发现在各种厚度的微通道以及滑移区域不同表面分数情况下，条纹纹理对应的横向和纵向表观滑移长度明显大于牛顿液体各自的有效滑移长度。仔细研究了剪切变稀流体在超疏水壁上的黏度分布，以描述表观滑移的机理。揭示了表观滑移长度随外加剪切速率变化的非单调行为。剪切变稀流体的这一重要特性被认为对黏度流动曲线的陡度敏感，从而为大幅降低微通道中的流动阻力提供了一种方法。
