Non-Surcharged Multi-Path Trapezoidal Integration Mode - Accusonic 8510+ series Reference Manual

Path position coefficient is obtained by interpolation from the following look-up table (from ISO 6416).

Non-Surcharged Multi-Path Trapezoidal Integration Mode

The flow computation in this mode is performed in a series of steps, following the principles set out in ISO
6416 for the "mid-section" method. Each step consists of determining the flow over a smaller cross-
sectional area or panel. The total flowrate in the conduit then becomes the sum of the individual panel
flows.
There are three basic types of panel:

Bottom panel which is bounded on the bottom by the bottom or bed of the conduit and on the top
by the lowest operating path.

Intermediate panel bounded on the top and bottom by consecutive operating paths that are not at
the same elevation.

Top panel bounded on the bottom by the highest operating path and on the top by the surface of
the water.
Each of these panels is bounded on either side by the walls of the conduit, whose dimensions and shape are
defined by the layer parameters. The actual area for each panel can therefore be a complicated computation
involving the calculation of the conduit widths at the paths which bound the panel (from interpolation
between the nearest layer widths), the calculation of the areas between these paths and the layer nearest
them (or between the paths if there is no layer between them), and the calculation of the areas between any
other layers which may lie between these paths.
The flow computation in the bottom panel is:
Q
Bottom
where: Area
The flow in the intermediate panel above the bottom panel is:
Q = Area
Int
Ratio of path depth below
surface to depth of water
above bottom
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.95
 Vel  (1 + Bottom friction) /2
= Area
Bottom A
= conduit area between the bottom (Layer #1) and the lowest good path
Bottom
(or pair of crossed paths)
Vel = Water velocity as computed from the lowest good path or pair of crossed paths
A
 (Vel
+ Vel ) /2
Int A B
Ratio of point velocity to mean
velocity in the vertical
0.846
0.863
0.882
0.908
0.937
0.979
1.039
1.154
1.424
1.65 (extrapolation)
Flow Computation 3-3