How will this work in an unfixed domain? A domain with no walls, as some of their visualisations seem to use the walls to generate the field.
I thought rip currents (known popularly as rip "tides") were pretty well understood, and it has nothing to do with this "tractor beam" effect: http://en.wikipedia.org/wiki/Rip_current
Great, now do the same trick with sound pressure waves in air!
I bet that would make a deep rhythmic noise as it operated.