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