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