The intake opening, the propulsion device, and the conduit define {HEAD ~ a flow path} for {TAIL ~ the flow} of air and particulates and in one embodiment, the flow path has an approximately constant flow area from the intake opening to the propulsion device 
The intake opening , the propulsion device , and the conduit define { HEAD ~ a flow path } for { TAIL ~ the flow } of air and particulates and in one embodiment , the flow path has an approximately constant flow area from the intake opening to the propulsion device
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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH