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