Several such helicoid structures are combined with their radii overlapping, for the most effective interception of {HEAD ~ a certain cross sectional area} of {TAIL ~ the fluid flow} 
of
Several such helicoid structures are combined with their radii overlapping , for the most effective interception of { HEAD ~ a certain cross sectional area } of { TAIL ~ the fluid flow }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL