This radius R is selected in such a way that {HEAD ~ the flow} comes into {TAIL ~ contact} with the wall and thus causes the swirl coefficient to increase considerably 
comes into
This radius R is selected in such a way that { HEAD ~ the flow } comes into { TAIL ~ contact } with the wall and thus causes the swirl coefficient to increase considerably
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH