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