Watershed Engineering or SWMM5

SWMM 3,4 to 5 Converter Interface
The SWMM 3 and SWMM 4 converter can convert up to two files at one time to SWMM 5. Typically you would convert a Runoff and Transport file to SWMM 5 or a Runoff and Extran File to SWMM 5. If you have a combination of a SWMM 4 Runoff, Transport and Extran network then you will have to convert it in pieces and copy and past the two data sets together to make one SWMM 5 data set.

The x,y coordinate file is only necessary if you do not have existing x, y coordinates on the D1 line of the SWMM 4 Extran input data set.



You can use the command File=>Define Ini File to define the location of the ini file. The ini file will save your conversion project input data files and directories.



You can use the command File=>Define Your Text Editor to define the location of the text editor program. The ini file will save your conversion project editor name.



You can get a copy of the latest SWMM 3,4 to 5 Converter Here..

Purpose: The purpose of this note is to explain a significant dynamic wave routing difference between EPA SWMM 5.0.013 and EPA SWMM 5.0.011 and before. A few people have detected a difference. The previous solution(s) would use only the midpoint area (Amid) and hydraulic radius (Rmid) in the dynamic wave solution. The new solution will use a slider or linear combination of the midpoint area (Amid) and hydraulic radius (Rmid) and the upstream cross sectional area (A1) and hydraulic radius (R1). The slider is based on the Froude number in the link. The change involves the A and R link spacing in the two dominant terms of the St. Venant Equation:


The new method is a linear combination or slider that weights the value of A and R in the St. Venant Equation based on the value of rho (), or



where, Rho () is a function of the Froude number. The effect of this addition is that as the Froude number increases from 0.5 to 1.0 and beyond the area and hydraulic radius used as the pivot point in the St. Venant equation moves from the midpoint of the link to the upstream end of the link. When the Froude number is above 1.0 the St. Venant and Normal Flow equation both use the same cross sectional area and hydraulic radius which makes for a more stable model.

Just for reference, the equation for Qnorm or the Manning's Equation flow is



The equations for the calculation of Rho () as a function of the Froude Number (Fr) are:



If ALL of the follow conditions are true Rho ()is calculated:

• the pipe is not full,
• h1 >= h2, and
• qLast > 0.

where,
h1 is the head at the upstream end of the link,
h2 is the head at the downstream end of the link and
qLast is the last flow value in the link.

If any of these conditions are true then rho = 1.0 and the value of A and R are the values Amid and Rmid, respectively.
The next graph shows the relationship between Rho and the Froude Number.



The value of Awtd and Rwtd move from the midpoint of the link to the upstream end of the link as the Froude number increases from 0.5 to 1.0.




Conclusion: This change should make the solution more stable because there is no longer an oscillation between the St. Venant Equation A and R and the Normal Flow Equation A and R.