I have been working on a new knowledge pattern project that maps the flow over a surface. The bigger project is to develop a new form of tiling that incorporates performance into the patterning and surface subdivision. In the first series below, you can see the various steps to the flow pattern (the original surface, the first knowledge pattern that creates a set of isocurves, and then the lines of flow based on the difference between vertical and the surface normal at that intersection.
Below are a couple of variations as the surface is manipulated. The next immediate step is to capture the lengths of the lines and possibly vary the line weight to better graphically represent the impact of slope. (click the image for a larger view)
Another iteration. (click for larger view)
Below is an obvious example of water moving across a surface. The Lotus Leaf surface is "hydrophobic", keeping it clean because of its ability to repel water.