{HEAD ~ A vortex shedding flowmeter} uses two ultrasonic transducers to generate an acoustic beam at {TAIL ~ a selected carrier frequency} 
{ HEAD ~ A vortex shedding flowmeter } uses two ultrasonic transducers to generate an acoustic beam at { TAIL ~ a selected carrier frequency }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL