How Telsa came up with most the things he did are beyond me. I have always thought he was the smartest man that has ever lived.
No doubt that Tesla was a bright person though.
In the field of fluid dynamics, it is referred to as a check valve. [1][2]
[1] http://en.wikipedia.org/wiki/Check_valve
[2] http://www.spiraxsarco.com/resources/steam-engineering-tutor...
But those sources you list describe several types of check valves, all of which have moving parts.
There might be some interesting applications for a device that passes two things, say a fluid and a gas, in one direction and resists the fluid (but not the gas) in another.
Most all check valves use moving parts; the Tesla Valve is novel because it does not.
I added the sources for those that might want to satisfy their curiosity when thinking, "I wonder what type of device a Tesla Valve is?"
Although the Tesla Valve does not use moving parts, that does not mean that it is not classified as a check valve. Tesla's descriptions from his patent [1] describe the valve as only permitting flow through it in one direction, which is the essential operation of a check valve:
"[...] a series of recesses or pockets with surfaces that reverse a fluid tending to flow in one direction therein and thereby check or prevent flow of the fluid in that direction." (Page 5, Item 3)
"[...] and thereby check their progress when impelled in the opposite sense." (Page 5, Item 5)
"[...] reverse such fluid impulses when impelled in the opposite direction and check their flow." (Page 5, Item 6)
Easy to dismiss genius - it all seems so obvious now!
So people tend to downvote witty comments unless they find them very funny.