The characteristics of a surface can have a major impact on the form a flow takes. The photo above shows a corrugated, almost pinecone-like water surface. It’s the result of a sheet of water flowing over a surface with alternating bands of hydrophobic (water-repelling) and hydrophilic (water-loving) properties. The water sheet narrows over hydrophobic sections and expands over hydrophilic ones. Gravity, inertia, and surface tension compete to create the overall braided appearance. You can see a top-down view of the flow in the original poster. (Image credit: M. Grivel et al., source)
Corrugating Water
