| |
| Wall slip for a fluid flowing near a randomly nanorough surface can be described by a hydrodynamic equation subjected to wall slip control equations. The problem is solved using a surface limiting shear stress model and complementary algorithm. It is found that, for the roughness effect on the hydrodynamic force of two approaching surfaces, definition of zero separation of rough surfaces is very important. Different definitions of the zero separation may give rise to different conclusions in both the cases of slip and no-slip. The theoretical predictions are compared with the experimental observations for both smooth surfaces and rough surfaces. For smooth surface, a very good agreement exists between theory and experiment. For rough surfaces, it is found that roughness increases the boundary slip if the zero separation is defined at the roughness peaks. This agrees with the experimental observation by Bonaccurso, Butt and Craig (Phys. Rev. Lett. 2003, 90(14), 144501). |
|
| Keywords:roughness, wall slip, fluid flow |
|
