Drag reduction using metallic engineered surfaces with highly ordered hierarchical topographies: nanostructures on micro-riblets

- Top-down fabrication method for ordered metallic nanostructures on micro-riblets.
- Combining the drag-reduction effects of ordered nanostructures and micro-riblets.
- Drag reduction enhancement by coexistence of air entrapment and riblet effects.
- Investigation of the drag-reduction property of fabricated metallic surfaces.