Open Channels And Partially Full Pipes (When More Than One Path Is Submerged; Pipes And Channels Where Only One Path Is Submerged - Accusonic 8510+ series Reference Manual

A-4 Multiple-Path Transit-Time Flowmeters Principle of Operation
Open Channels and Partially Full Pipes (When More Than One Path is
Submerged)
Where:
Q = flowrate
A = Cross sectional area (determined as a function of depth and channel/pipe dimension
V = Velocity of lowest path of lowest pair of crossed paths
A
F = FBottom friction coefficient
Bottom
V = FVelocity of the I path or pair of crossed paths
i
W = FWeight for the surface velocity to correct for friction at the surface
Top
V = FSurface velocity extrapolated from the top two measured path velocities.
Surface

Pipes and Channels Where Only One Path is Submerged

Where:
A = Cross-section area of flow (depth)
C = A correction factor to correct velocity measured as a function of the path height to depth. The
correction factor is based on USGS (ISO 6416) developed velocity/depth relationships.
In cases where there is a very short (less than 5 x width or diameter) straight channel or pipe run upstream
of the meter section, it is likely that the direction of flow will not be parallel to the centerline. If this is the
case, a second crossed path at each elevation will be required to eliminate the cross-flow error (Fig. 5).