MEchanics GAthering –MEGA– Seminar: Influence of porous flow on dip coating of a rough surface

Surface roughness significantly modifies the liquid film thickness when dip coating a solid surface at low velocity. To investigate the relative importance of slip atop the roughness compared to flow through the textured layer, we experimentally measure film thicknesses deposited on surfaces with roughness resembling disconnected pores in comparison with porous surfaces that allow flow through the textures. Here, the film thickness is calculated by modeling the flow with a homogenized boundary condition at an equivalent flat surface between the porous region and outer film, which accounts for both flow through the porous layer and slip at the equivalent surface. The model is found to agree with experimental data and requires no fitting parameters. Furthermore, our model may be applied to arbitrary periodic roughness patterns, facilitating characterization of surfaces found in natural and industrial coating processes.