The ratio between the fixed intake aperture, and {HEAD ~ the configurable exhaust aperture} creates a volume and thus a velocity differential in {TAIL ~ the air mass} on either side of the relatively centrally located in the duct turbine type fan, 3 
The ratio between the fixed intake aperture , and { HEAD ~ the configurable exhaust aperture } creates a volume and thus a velocity differential in { TAIL ~ the air mass } on either side of the relatively centrally located in the duct turbine type fan , 3
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH