Abstract

Micro- or nanostructured surfaces can provide a significant slip to a fluid flowing over the surface, making them attractive for the development of functional coatings. This slip is due to a second fluid being entrapped in the indentations of the structured surface, like air for superhydrophobic surfaces or oil for so-called lubricant-infused surfaces (SLIPS). This talk addresses the flow phenomena close to such surfaces. The nature of the structured surface leads to a mixed-boundary value problem for the flow field, which, for the considered situation, obeys the biharmonic or Laplace equation. Using complex variables techniques, a solution to this problem can be found, such that simple, explicit expressions for the flow field as well as the effective slip length of the surface can be found. They can for example be employed as a guideline to design efficient surface coatings for drag reduction. This is work together with Steffen Hardt (TU Darmstadt).