Energy is extracted from a free stream fluid flow of wind or water by means of {HEAD ~ a multi turn helicoid structure} with {TAIL ~ a relatively small pitch angle} 
with
Energy is extracted from a free stream fluid flow of wind or water by means of { HEAD ~ a multi turn helicoid structure } with { TAIL ~ a relatively small pitch angle }
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 TAIL TAIL