{HEAD ~ The oscillating flow components} are detected with {TAIL ~ a pair} of ultrasonic transducers defining an acoustic path intersecting the vortices 
are detected with
{ HEAD ~ The oscillating flow components } are detected with { TAIL ~ a pair } of ultrasonic transducers defining an acoustic path intersecting the vortices
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH