My first attempt at a vortex diode just kind of worked:http://www.thingiverse.com/thing:96480

But I wanted better. So I more than doubled the radius.

Properties:blowing in one direction is harder than the other. You can find out more at my blog:

http://mymakerblog.wordpress.com/2013/05/31/fluidic-diodetrials-and-tribulations/

So the picture is a bit wonky because I forgot the mouth piece in the top piece. That problem is fixed in the current version. The print comes in two pieces and you have to glue them together.