junction losses

1. how does swmm handle junction losses when NEQUAL is set to 1

2. The version of SWMM I am using (CSWMM 2002beta) only has an option of setting NEQUAL to 1, 2, or 3. I have read through some of the Q & A and read that there is actually the option of setting NEQUAL from 1 to 5. what will numbers 4 and 5 do

3. is there a standard entrance or exit or other loss coefficient that is applied to a manhole whether it be straight through or at a 90degree bend or that the upstream conduit is at 5% and down stream is at .03% Etc...... some of the other modeling programs I have worked with gave u the option of using various methods such as ASSHTO, assumed, approximate ETC. In the past I have calculated various junctions by hand and know that there can be significant losses but I am new to SWMM and would appreciate some guidance.

Thanks in advance
JT

Dear JT,

An abbreviated version of what the NEQUAL parameter does:

Nequal=1 Create equivalent conduits based on the COURANT condition (no local losses)
Nequal=2 Create equivalent conduits based on incorporating local losses no lengthening
Nequal=3 Create equivalent conduits based on incorporating local losses and on the COURANT condition
Nequal=4 Local losses read from C1 lines are factored into momentum equation (no lengthening)
Nequal=5 Local losses read from C1 lines are factored into momentum equation and conduits are lengthened based on COURANT condition.

Now, on to your questions:

1. how does swmm handle junction losses when NEQUAL is set to 1
---> It does not handle junction losses when NEQUAL is 1 except if you alter the roughness of the conduit to account for entrance and exit losses

2. The version of SWMM I am using (CSWMM 2002beta) only has an option of setting NEQUAL to 1, 2, or 3. I have read through some of the Q & A and read that there is actually the option of setting NEQUAL from 1 to 5. what will numbers 4 and 5 do
---> See above

3. is there a standard entrance or exit or other loss coefficient that is applied to a manhole whether it be straight through or at a 90degree bend or that the upstream conduit is at 5% and down stream is at .03% Etc...... some of the other modeling programs I have worked with gave u the option of using various methods such as ASSHTO, assumed, approximate ETC. In the past I have calculated various junctions by hand and know that there can be significant losses but I am new to SWMM and would appreciate some guidance.
--> I have found that since SWMM has the same loss formulation K*V^2/2g that bend losses or other loss coefficients found by your equations can be used directly in SWMM. The coefficients are transferable.

For XP-SWMM users please note that the above does not apply to you. In XP-SWMM the value of NEQUAL is the time step you want to use to lengthen the short pipe. If NEQUAL is 5 then a five second time step is used to check for pipes to lengthen. If the courant condition is exceeded based on the five second value then the pipe is lengthend. Entrance, exit and other losses are used or not used independently of the value of NEQUAL.

Best Regards,
Robert Dickinson
dickinsonre@cdm.com