Hey I was just looking at some of my favorite images.
Specifically scroll down about 1/10 of the length down this page, and see the picture with the egg in the stream, creating longitudal vortexes. This is probably equal in power to a flowform.
here is the link Schauberger page
- see fig. 11.4
Bill Mollison also talks about Flowforms in the Permaculture Handbook, he suggest making them concrete or Glass Reinforced Plastic - I assume he means Fiberglass...
You could probly make a mold out of Dirt, then pour concrete over the shape in the dirt, let it dry, and clean the dirt out of the bottom part when its dry.
Cheers, take care of your waters