The casing 30 and the collar 40 also form {HEAD ~ a smooth and curved outer shape} so as to reduce {TAIL ~ the turbulence} 
to reduce
The casing 30 and the collar 40 also form { HEAD ~ a smooth and curved outer shape } so as to reduce { TAIL ~ the turbulence }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL