The accelerated positively charged ions accelerate low energy air within lower regions of a boundary layer over {HEAD ~ the ducted surfaces} bounding {TAIL ~ the ducted fluid flow} 
bounding
The accelerated positively charged ions accelerate low energy air within lower regions of a boundary layer over { HEAD ~ the ducted surfaces } bounding { TAIL ~ the ducted fluid flow }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL