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