What is Flow Profile?

The above animation is an example showing that fluid flowing in a pipe does not move at the same velocity of every cross sectional area of the pipe . This behavior is describe as Newtonian. To simplify matters, most flow measurement applications are Newtonian. In layman’s terms, they are fluids which move more slowly  in the outer sides of the pipe than in the middle.  Non Newtonian fluids do not necessarily behave in this way and have  a more unpredictable behavior.

The following Flow Calculator predicts the Reynolds Number which relates to the Flow Profile. Note the important inputs the Reynolds Calculator needs to know. These are Pipe Diameter, Fluid Velocity, Density and Viscosity.

 A fluid moving with a lower Reynolds Number is classified as Laminar Flow e.g  thick Oil at a low Flow Rate while water at the same velocity has a higher Reynolds Number and is called a turbulent Flow.

There is a very common misconception regarding these terms. For some reason these terms have been  mixed up and confused in non in depth pipe flow measurement discussions.

A simplified textbook discussion relating Reynolds numbers defines the lower Reynolds numbers as Laminar and higher ones as Turbulent and Reynolds numbers in between as Transitional.  

Manufacturers of high quality  inferential volumetric oil flowmeters  (measuring velocity) as opposed to direct measurement (PD Volume Meters) will use the calculated Reynolds number of the moving fluid as a correction factor in their software when the fluid is below or above certain velocities. 

Large Bore Magmeter will measure water in Turbulent Flow at both high and low velocities

Fortunately for most general industrial flowmeter manufacturers, the turbulent flow Regime is found in almost all of the standard applications e.g water flow meters-

which simplifies the flowmeter software and production/calibration of their products.

There are also other factors not being discussed here that may affect the flow of the profile including the roughness of the pipe, the direction of flow (e.g. up or down) and the effects of pipe bends , amount of straight length of the pipe and objects protruding into the pipe which may cause some flow profile disturbance and other factors which are for more deeper discussions.

HIGHER ACCURACY FLOW MEASUREMENT

Meter Prover

Certain industries require a much higher accuracy and repeatability in their flow measurement devices  than other general industry applicatons since the measurement might be considered to be more critical as opposed to having a general indication of flow. Examples of this might be controlled mixing of chemicals or custody transfer metering for products like crude oil or natural gas where errors in flow measurement will cause a dispute between buyer and seller.  The flow measurement systems for example in oil and gas applications could involve live inputs from other devices measuring density, temperature and even composition of product

This article was produced in an effort to simplify what is understood as Flow Profile and its importance in Flow Measurement. If you have any suggestions on how it can be improved or if you would like to make a separate contribution please contact webmaster@flowmeterdirectory.com

UNITS OF FLOW MEASUREMENT