An impeller is mounted in the trailing end of the concavity and {HEAD ~ a stator} trails {TAIL ~ the impeller} 
trails
An impeller is mounted in the trailing end of the concavity and { HEAD ~ a stator } trails { TAIL ~ the impeller }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL