Schauberger
It was Viktor Schauberger's customary practice to seek immediate patent cover for all his inventions and devices, of which the following principally concern those related to water. Unfortunately, just about all of the patents he applied for during World War II are no longer available and therefore, while his various devices are described in a number of his writings, no visual representation of them exists. This makes their proper description an extremely difficult task. - Editor [The Water Wizard]

Many suggestions have already been made as to how losses in energy, pressure or velocity arising in the transport of liquids or gaseous media can be reduced. Thus for the purposes of inhibiting the formation of air-bubbles, which provoke an increase in the resistance to flow, a British Patent No. 409,528 for a pipe has been published, which is wound in a screw-form manner and its cross-sectional surfaces are formed by two arcs of a circle. From the British Patent No. 28,5343 of 1913 AD, the application of a pipe with an egg-shaped cross-section was made known, which was provided with flow-directing slats to inhibit the formation of vortices. In the U.S. Patent No. 1,655,197 as well as in the Schauberger - Swiss Patent No. 126637, cylindrical or conical pipes were proposed with the object of reducing friction by converting it into rotation, for which the pipe axis served as the rotational axis. Lastly, the Schauberger - Austrian Patent No. 28099 depicts the use of indented and twisted pipes. [The Energy Evolution - Harnessing Free Energy from Nature, Schauberger Patent 196680 - Pipe for Liquid and Gaseous Media]

Schauberger Patent 136214
Schauberger Patent 113487
Schauberger Patent 117749
Schauberger Patent 142032
Schauberger Patent 138296
Schauberger Patent 134543
Schauberger Patent 196680 - Pipe for Liquid and Gaseous Media

A more complete list of his patents: http://www.rexresearch.com/schaub/schaub.htm