Inelastic non-Newtonian flow over heterogeneously slippery surfaces
Inelastic non-Newtonian flow over heterogeneously slippery surfaces
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DOI：
10.1103/physreve.95.023105
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发表时间：
2017-02-09
影响因子：
2.4
通讯作者：
Lammertink, Rob G. H.
中科院分区：
文献类型：
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作者：
Haase, A. Sander;Wood, Jeffery A.;Lammertink, Rob G. H.
在这项研究中，我们研究了不均匀光滑表面上的非弹性非牛顿流体流动。首先，我们模拟了黄原胶水溶液在气泡垫上的流动，气泡垫是一个超疏水表面，由横向定位的无滑移壁和无剪切气泡组成。结果表明，对于剪切稀化流体，只要系统在剪切稀化状态下运行，壁滑移就会显着增加。对于幂律指数 n = 0.4 的 0.2 wt% 黄原胶溶液，数值结果表明，与牛顿液体相比，壁滑移可增强 3.2 倍。该增强因子也是根据理论分析预测的，该分析给出了在平坦、不均匀的光滑表面上可以获得的最大滑移长度的表达式。尽管该方程是针对远大于系统典型尺寸的无滑移/无剪切单位长度推导的，但我们发现它也可用于预测滑移长度与无剪切区域大小或气泡宽度成正比的区域的增强。结果可以与系统的流体动力学发展或入口长度耦合，因为只有当流体流动能够完全适应壁上的无滑移和无剪切条件时才能达到最大壁滑移。
In this study, we investigated inelastic non-Newtonian fluid flow over heterogeneously slippery surfaces. First, we simulated the flow of aqueous xanthan gum solutions over a bubble mattress, which is a superhydrophobic surface consisting of transversely positioned no-slip walls and no-shear gas bubbles. The results reveal that for shear-thinning fluids wall slip can be increased significantly, provided that the system is operated in the shear-thinning regime. For a 0.2 wt% xanthan gum solution with a power-law index of n = 0.4, the numerical results indicate that wall slip can be enhanced 3.2 times when compared to a Newtonian liquid. This enhancement factor was also predicted from a theoretical analysis, which gave an expression for the maximum slip length that can be attained over flat, heterogeneously slippery surfaces. Although this equation was derived for a no-slip/no-shear unit length that is much larger than the typical size of the system, we found that it can also be used to predict the enhancement in the regime where the slip length is proportional to the size of the no-shear region or the bubble width. The results could be coupled to the hydrodynamic development or entrance length of the system, as maximum wall slip is only reached when the fluid flow can fully adapt to the no-slip and no-shear conditions at the wall.