1. Design of a Pipe 7
101
Runoff 102 1
Link 101 8
Inflow 102
102 9
Outflow 101 2
Link 102 3 10
103 11
Outflow 102 4 5 6
In a tree network, each node can have only one outflow link. Therefore we use the convention that link numbers are the same as the upstream node number.

2. Get the Maximum Inflow
If no inflow hydrograph exists the user can specify a peak flow for the design
Use Hydrograph|Add Runoff to update Inflow hydrograph

3. Uniform Flow in Pipes
Solve for y0 using

4. Critical Depth in Pipes
Solution for Ycr is based on the minimum energy criterion

5. A Trial Pipe Design Table of feasible designs for given Q and ‘n’
Double click on a row to test trial design
Click [Design] to get results of part-full flow analysis

6. Surcharged Pipes Due to closed top boundary resistance increases
as depth y approaches diameter D.
At y = D Q = Qfull
Q/Qfull
When y = D Q = Qfull.
y/D

7. Surcharged Pipes Q > Qfull Q = Qfull Q < Qfull
Energy line
Q > Qfull
Water surface
Q = Qfull
Q < Qfull
MIDUSS 98 assumes uniform flow for part-full pipes

8. Exercise 4
Design a pipe to carry 2 c.m/s when running 75% full with a gradient of 0.4% and n = 0.013
Check for surcharged hydraulic grade line if discharge increases to 3 c.m/s