The apparatus 1 wherein the flow obstruction comprises a plurality of bluff bodies and {HEAD ~ the oscillating flow components} are produced from {TAIL ~ vortices} shed from the bluff bodies 
are produced from
The apparatus 1 wherein the flow obstruction comprises a plurality of bluff bodies and { HEAD ~ the oscillating flow components } are produced from { TAIL ~ vortices } shed from the bluff bodies
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH