Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
J Chem Phys. 2011 Nov 28;135(20):204704. doi: 10.1063/1.3663384.
The influence of periodic and random surface textures on the flow structure and effective slip length in Newtonian fluids is investigated by molecular dynamics (MD) simulations. We consider a situation where the typical pattern size is smaller than the channel height and the local boundary conditions at wetting and nonwetting regions are characterized by finite slip lengths. In the case of anisotropic patterns, transverse flow profiles are reported for flows over alternating stripes of different wettability when the shear flow direction is misaligned with respect to the stripe orientation. The angular dependence of the effective slip length obtained from MD simulations is in good agreement with hydrodynamic predictions provided that the stripe width is larger than several molecular diameters. We found that the longitudinal component of the slip velocity along the shear flow direction is proportional to the interfacial diffusion coefficient of fluid monomers in that direction at equilibrium. In case of random textures, the effective slip length and the diffusion coefficient of fluid monomers in the first layer near the heterogeneous surface depend sensitively on the total area of wetting regions.
通过分子动力学（MD）模拟研究了周期性和随机表面纹理对牛顿流体流动结构和有效滑移长度的影响。我们考虑了一种情况，其中典型的图案尺寸小于通道高度，并且润湿和非润湿区域的局部边界条件的特征在于有限的滑移长度。在各向异性图案的情况下，当剪切流方向相对于条纹方向不对准时，报告了流过不同润湿性交替条纹的横向流动剖面。从 MD 模拟获得的有效滑移长度的角度依赖性与流体动力学预测吻合良好，前提是条纹宽度大于几个分子直径。我们发现，沿剪切流方向的滑移速度的纵向分量与平衡时该方向上流体单体的界面扩散系数成正比。在随机纹理的情况下，靠近非均匀表面的第一层中流体单体的有效滑移长度和扩散系数对润湿区域的总面积敏感。
