ChannelFlow: Pipe
Input Parameters:
name Text of up to 10 characters. Blanks are not allowed. This is in order to preserve the tabular printout, which can be read back into the program.
Q# Flow in section. This can reference a flow computed on a "Qcia" line.
D Inside diameter.
dy Vertical inside diameter, used only for elliptical pipe. If left as zero, a circular pipe is assumed.
InvIn Elevation or invert of the pipe at the inlet. It can be left zero. The inverts are used only with the length to compute the slope. If a slope is given, they are unnecessary for computation.
InvOut Elevation or invert of the pipe at the outlet. It can be left zero. The inverts are used only with the length to compute the slope. If a slope is given, they are unnecessary for computation.
L Length of the pipe. It can be left zero. It is used only with the inverts to compute the slope. If a slope is given, length is unnecessary for computation.
S Slope of the pipe. If inverts and length are given, this value will be computed.
n Manning's roughness coefficient. Suggested values are given with the Open Channel formulas.
Output:
V Average velocity of flow.
d Depth of normal flow.
dc Critical flow depth.
Qf Flow required for full flow. This is used as the capacity, even though a slightly higher flow can be acheived by a depth not quite equal to full flow.
t Flow time through the pipe. Length / average velocity.

Properties for a pipe flowing partially full are computing with the following formulas;

Dimensions for ellipses are approximated by taking sums to solve the following integrals, shown below with a sketch of the elliptical section considered.

In some cases, the program may indicate warnings for flow beyond capacity when the pipe is actually not full. This is because the warnings are triggered by a given flow being more than what is possible when the pipe is full, which is a good design assumption. However, because of the relationship between wetted perimeter and flow area, a pipe slightly less than full can actually accommodate more flow, thus creating the apparent inconsistency.

(return)