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