Air Knives Explained
or, "Dude, where's my curtain transvector?"
"Air Knife" is the more common name for a curtain transvector. The air knife accelerates and amplifies the airflow coming into it, just as a nozzle would, but also transforms the turbulent inflow into a laminar planar outflow. This means that you have a jostling, unstable cylinder of air (whose shape is constrained by the pipe or hose the air travels in) for the input, but your output is a wide, flat sheet (or "knife") of air that retains its shape over several feet, with no external influence.
or, "Laminar? I hardly even know 'er."
Air knives have several industrial uses. They can be used to dry anything moving by on a conveyor belt, especially where the objects to be dried are wide, or there is insufficient space in the assembly line to store them for normal drying. They can replace conveyor belts for tiny parts--picture tiny computer case screws in a wide but shallow stainless steel trough. With an air knife behind them, they could be blown several feet down the line. You can also use the tight ribbon of air to clean off items that you don't want to expose to a water wash.
...that you might actually care about.
The real strength of an air knife lies in its ability to use air from somewhere other than its location; this means you can use air that's been heated or cooled (from the building's air conditioner or heater) or even air that's been ionized! The latter is useful for removing static electricity from electronic parts before they are bagged and shipped--and I know how static-free you like your electronic parts. Heated (or chilled) air is useful for separating hot air from cold air. You've most likely encountered an air knife serving this purpose in a large store (like a grocery store, a Home Depot, or a Wal-Mart). The air knife is placed over the top of the building's main door, and when the door is opened, the air knife turns on, putting a barrier of swiftly-moving air between the uncomfortable outside environment and the wonderfully temperate indoor climate. This works equally well in summer or winter; all you need to do is run a hose from the outflow of your building's HVAC system straight into the air knife, and use a relay or infrared door opener switch to activate and deactivate the air knife. The cost of running the air knife is minimal compared to heating or cooling the external air that would normally "leak" into your building every time the door opened.
Yeah, so what?
Oh, I see how it is. Very well. The AIR KNIFE offers businesses the opportunity to save energy and money by further increasing man's control over the elements, and represents a stunning achievement in the field of applied fluid dynamics.
And I think they're pretty freakin' sweet.