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