
|
|
|
|
|
Applies To |
|
|
|
|
|
|
|
Product(s): |
Bentley SewerGEMS, Bentley CivilStorm, Bentley StormCAD |
|
|
Version(s): |
08.11.XX.XX |
|
|
Environment: |
N/A |
|
|
Area: |
|
|
|
Original Author: |
Mark Pachlhofer and Jesse Dringoli, Bentley Technical Support Group |
|
|
|
|
|
Problem
How does the StormCAD (GVF-Rational solver) calculate the velocity at a cross section node element?
Solution
For a cross section, the velocity corresponds to the downstream end of the upstream channel link, whose shape is determined by the next upstream cross section.
Example:

1. Take the flow reported in the link upstream of the cross section node you want to check the velocity on. In this example that is, 67.53 m^3/s for Channel -1.
2. Locate the bottom width of Channel-1, which is defined in cross sections-0 and is 1.250 m (The upstream node bottom width is used for the channel because channels are assumed to be prismatic in StormCAD). This will be multiplied by the Depth (Out) of Channel -1, which is 6.65 m.
3. Now divide the flow reported from step 1 by the value from step and that will give you the velocity at the downstream node, which in this example is 8.06 m/s at CS-1.
The equation looks as follows:
Q=VA
V=Q/A
V = (upstream link flow (Channel-1) \ (bottom width of upstream channel defined at it's upstream cross section (CS-0) * depth out of that channel (Channel -1)))
V = (67.53 m^3/s \ (1.250 m * 6.665 m))
V = 8.06 m/s