The cross section of flow of the tube 20 in this region is given {TAIL ~ a transition radius R}, {HEAD ~ the size} of which in principle depends on the flow inside the tube 20 
The cross section of flow of the tube 20 in this region is given { TAIL ~ a transition radius R } , { HEAD ~ the size } of which in principle depends on the flow inside the tube 20
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH