Reported data of measured slip lengths in nanostructures span several orders of magnitude, from a few nanometers to tens of micrometers. Small roughness on surfaces caused by structural defects or thermal fluctuations dramatically reduces slippage. Tiny bubbles entrapped on rough surfaces can also affect slippage. We used an asymptotic solution and a high density-ratio pseudopotential lattice Boltzmann model to systematically study the drag resistance of a rough surface with attached bubbles. As bubbles nucleate and grow, drag resistance is slightly reduced until the tri-phase contact line reaches the edges of roughness, where bubbles with small angles substantially reduce drag resistance. As bubbles grow to become a continuous gas layer on the surface, the drag resistance greatly decreases. However, the interface deformation from flat to curved shape greatly hinders liquid flow, and the vortex structures cause a wave-like fluctuation in the effective slip length. This finding sheds light on the controversies of reported large variations in the slip length of super-hydrophobic surfaces in nanostructures, e.g., carbon nanotubes.

中文翻译：

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重新评估疏水性纳米结构中的水滑移

报告的纳米结构中滑移长度的测量数据跨度从几个纳米到几十个微米不等。由结构缺陷或热波动引起的表面小粗糙度可大大减少打滑。残留在粗糙表面上的微小气泡也会影响打滑。我们使用渐近解和高密度比伪势格子Boltzmann模型来系统地研究带有气泡的粗糙表面的抗阻力。随着气泡成核并生长，阻力阻力会略微降低，直到三相接触线到达粗糙度边缘为止，在此处，具有小角度的气泡会大大降低阻力阻力。随着气泡的生长变成表面上的连续气体层，抗阻力性大大降低。然而，从平面形状到弯曲形状的界面变形极大地阻碍了液体的流动，并且涡旋结构在有效滑移长度上引起了波状波动。这一发现为报道的纳米结构（例如碳纳米管）中超疏水表面滑移长度的大变化带来了争议。