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