A popular way to mitigate this problem is to use multiple sensor pairs, sending acoustic signals
along multiple paths through the fluid (i.e. a multipath ultrasonic flowmeter), and to average the
resulting velocity measurements. Dual-beam transit-time flowmeters have been in use for well over
a decade at the time of this writing (2009), and one manufacturer even has a five beam ultrasonic
flowmeter model which they claim maintains an accuracy of ± 0.15% through the laminar-toturbulent
flow regime transition52. A simplified illustration of a Daniel four-beam (or four “chord”)
ultrasonic flowmeter is shown here: