Siemens SITRANS FUP1010 Operating Instructions Manual page 16

Description
3.3 Theory of Operation
∅° = sin
T
L
V
F
Flow Profile Compensation
Another important consideration is that the ultrasonic flowmeter has to compensate for the
flow profile to maintain calibration accuracy. Shown below is a graphic of a "fully-developed"
flow profile. Note that the fluid velocity increases toward the center (axis) of the flow stream.
①
Fluid velocity near the axis of the flow stream tends to be greater.
The Reynolds number is then computed as follows:
The flowmeter then uses this computation of Reynolds number to compensate the raw flow
velocity for conditions of laminar or turbulent flow profile as defined by an internal Reynolds
compensation table. The flowmeter then converts the compensated flow velocity to volumetric
flow rate.
Rate = V
14
(VOS / V )
-1
phase
= 2 * ID / (VOS * cos ∅)
= V * DT / (2 * TL)
phase
where viscosity = cS = cP/density
cS = kinematic viscosity
cP = absolute viscosity
* Comp(Rn) * Pipe area
F
Where: VOS = Velocity of sound in liquid
V
phase
ID = Pipe inside diameter
T = Transit time in liquid
L
DT = Measured Transit-Time difference
V = Flow Velocity
F
Operating Instructions, 02/2010, A5E02951522A Revision 01
= Phase velocity of sensor
FUP1010 IP67 Portable Flowmeter