Effective slip in pressure-driven Stokes flow
Effective slip in pressure-driven Stokes flow
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DOI：
10.1017/s0022112003004695
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发表时间：
2003-08-25
影响因子：
3.7
通讯作者：
Stone, HA
中科院分区：
文献类型：
--
作者：
Lauga, E;Stone, HA
最近在光滑的疏水表面上通过实验观察到纳米气泡，当使用部分润湿流体时，表面上的裂纹同样可以是气泡的位置。由于这些气泡可以提供零剪切应力边界条件，并大大修改固体边界产生的摩擦，它是感兴趣的数量的压力驱动流的影响，特别注意小的几何形状。本文研究了圆管中两种简单的定常压力驱动的Stokes流，圆管的表面包含周期性分布的零表面剪应力区域。在探测固体表面滑移的实验研究的精神，所得到的有效滑移长度如何被评估为描述表面不均匀性的自由度的函数，即无滑移和无剪切应力区域的相对宽度及其沿管道的分布沿着。该模型与毛细管和微通道中压力驱动流动的实验研究进行了比较，并对实验结果进行了可能的解释，这与大量分布的滑移域（如纳米尺寸和微米尺寸的近平坦气泡）涂覆在固体表面是一致的。此外，建议的可能性的剪切相关的有效滑移长度，并提出了一个解释的测量滑移长度随系统尺寸的增加，这是与实验结果一致的，似乎自相矛盾的行为。
Nano-bubbles have recently been observed experimentally on smooth hydrophobic Surfaces, cracks on a surface can likewise be the site of bubbles when partially wetting fluids are used. Because these bubbles may provide a zero shear stress boundary condition and modify considerably the friction generated by the solid boundary, it is of interest to quantity their influence on pressure-driven flow, with particular attention given to small geometries. We investigate two simple configurations of steady pressure-driven Stokes flow in a circular pipe whose surface contains periodically distributed regions of zero surface shear stress. In the spirit of experimental Studies probing slip at solid surfaces, the effective slip length of the resulting How is evaluated as a function of the degrees of freedom describing the surface heterogeneities, namely the relative width of the no-slip and no-shear stress regions and their distribution along the pipe. Comparison of the model with experimental studies of pressure-driven flow in capillaries and microchannels reporting slip is made and a possible interpretation of the experimental results is offered which is consistent with a large number of distributed slip domains such as nano-size and micron-size nearly flat bubbles coating the solid surface. Further, the possibility is suggested of a shear-dependent effective slip length, and an explanation is proposed for the seemingly paradoxical behaviour of the measured slip length increasing with system size, which is consistent with experimental results to date.