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