Grumpy_Mike:
Not quite, there is a change between linear flow and turbulent flow as the flow speed increases. Not all flow is turbulent.
not sure of the fluid under discussion, but laminar flow is not easily found in a pipe or duct.
you have turbulence after any transitions such as an elbo or change in diameter. you have turbulence after a pump or valve.
as the fluid interacts with the wall of the pipe, you have a boundary layer and that moves slower the closer you get to the wall until the molecules at the wall may not even be moving. of course the center of the pipe is moving rapidly.
you can calculate this, google Reynolds Number.
after an elbo, you may need 50 diameters of pipe before the flow becomes laminar.
and of course there are methods/devices that will create a short distance of laminar flow for the purpose of measuring.
a flow straightener device for the fluid being used should be available.
google laminar flow nozze for water pumping on water fountains.
as for calibration, one might use an ASME nozzle and measure the pressure drop to determine the flow.
most (all?) manufactires of flow sensing devices have test aparatus to verify the readings, and most use an ASME nozzle because it is a fundamental sensor.