It is obtained by adding {HEAD ~ flow diverters} surrounding a helicoid structure with {TAIL ~ vertical axis} 
It is obtained by adding { HEAD ~ flow diverters } surrounding a helicoid structure with { TAIL ~ vertical axis }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL