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