Multi-Path Design; Flow Profile - Panametrics Sentinel User Manual

1.5.3

Multi-Path Design

Multi-path ultrasonic flowmeters are designed with more than one pair of transducers to interrogate the flow field in
different locations and more accurately determine the actual flow rate. The Sentinel Measurement System uses two
measurement locations. Both measurement paths are located along a diameter of the meter body and tilted at an
angle. The two measurement paths are orthogonal to each other (see Figure 3 on page xiv).
1.5.4

Flow Profile

One of the main factors affecting an ultrasonic flow measurement is the flow profile. If the flow profile is known,
mathematical modeling of the flow and the relationships between the paths' raw data can be made. This justifies the
required use of a flow-conditioning device with this system. A simulation example of how the flow conditioner
reduces secondary flow is shown in Figure 4 below. Maintaining a constant flow-profile shape across all flow
velocities, pipe sizes and upstream flow disturbances is difficult. For this reason, the factory has tested the Sentinel
under various conditions in an effort to determine its operational limits.
Disturbance Element
Strong Cross Flow
Sentinel™ User's Manual
Irregular
Velocity
Profile
Vz
5 D
Vx, Vy
Flow Conditioner
Figure 4: Using a Flow Conditioner to Influence Flow Profile
10 D
Vx, Vy  0
Cross Flow is Eliminated
Chapter 1. Installation
Regular
Velocity
Profile
Vz
y
z
x
5