Recommendations for minimum upstream and downstream straight-pipe lengths vary
significantly with the nature of the turbulent disturbance, piping geometry, and flow element. As a
general rule, elements having a smaller beta ratio (ratio of throat diameter d to pipe diameter D) are
more tolerant of disturbances, with profiled flow devices (e.g. venturi tubes, flow tubes, V-cones)
having the greatest tolerance22. Ultimately, you should consult the flow element manufacturer’s
documentation for a more detailed recommendation appropriate to any specific application.
In applications where sufficient straight-run pipe lengths are impractical, another option exists
for “taming” turbulence generated by piping disturbances. Devices called flow conditioners may be
installed upstream of the flow element to help the flow profile achieve symmetry in a far shorter
distance than simple straight pipe could do alone. Flow conditioners take the form of a series of
tubes or vanes installed inside the pipe, parallel to the direction of flow. These tubes or vanes force
the fluid molecules to travel in straighter paths, thus stabilizing the flowstream prior to entering a
flow element:
Velocity profile Velocity profile
(symmetrical)
pipe wall
(asymmetrical)
pipe wall
Flow condi