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is sewergems using a linear reservoir method or a non linear reservoir ?

hi guys and thank you very much for the great replies everytime and the coolest is the replies are fast lol

anyways

in my last report in univ am doing modelisation on a sewer network to see where will be flooded and also compare mathematic results with the reality results ( ofc when same storm intensity occure )

so i have to stat wot method am using

for example in french they call em ( (1 ) les fonctions de production , (2) fonctions de transfer ,(3) fonction d'acheminement ) 

1 = something like horton and scs methods , am not sure if i can call the IDF one of em

(2) reservoir lienar , non linear reservoir ( ti's actually something to convert the hydrograph on the catchement to a hydrograph in the sewer if am not mistaken

(3) is the implicit or explicit method

so if you know how to call em in english pls tell me :pand what method sewergems is using in (2) 

also am doing:

[rational method ( explicit) vs ( modified RM ( implicit) vs scs unit hydrog dimensionless in both ( implicit and explicit)

and see if there will be the same reults ( mean volume in outlet and if same MH get flooded or not and ofc compare with the reality results ( and the close one will use it in the future to detect where the flood will be

so what you guys think about this?

it is really useless comparaison? 

or ti's somethong good for someone who want to learn for now and get a conclusion

and so sorry for the too many questions Smiley

and if i have no reality data wot method you guys think is the close one usually ? or it's depend ? 

also is the SCS united hydrograph is suited for urban area sewers too ? devloped i mean with CN 98

and are you guys taking (0,2*S or 0,05*S ???)

and sorry again ^^

cordially . 

Parents
  • Hello Nei. 

    Are you modeling a combined storm - sewer modeling system as you want to model runoff for a sewer system? 

    The use of rational method / modified rational method or SCS unit hydrograph method depends upon your analysis type. E..g. do you want to model peak flows then you would go for rational method, which is applicable for GVF-Rational solver and if you want to go for fully dynamic flood hydrographs then you can go for MR or SCS UH method, however each method is different and results are not comparable. Selection of type of runoff method would depend upon designing engineer. 

    Why don't CivilStorm results for peak flow closely match StormCAD results for peak flow?

    Whether SewerGEMS uses linear or non-linear reservoir method, we will confirm this and respond. 

    In SewerGEMS 0.2 * S is taken for calculations, please search for SCS CN Runoff equation in help documentation for details on this.

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • thank you verry much for that help

    ye i will compare the hydrographs of catchments by using only MRM vs SCS united hydrograph

    oen mroe question can i run a simulation of SCS united hydrograph on ( implicit & explicit to compare results of flood routing ) ?

    bcoz am doing like hydrology then hydraulics and compare each one and comment why there's a different

    sadly i got no real values of volumes in my sewers to see which is close Stuck out tongue

    and am waiting if u guys are using linear or non linear reservoir

    and please agaaaain :3when the sewer is in charge wot method u guys are using ( INSA or others ? )

    cordially .

Reply
  • thank you verry much for that help

    ye i will compare the hydrographs of catchments by using only MRM vs SCS united hydrograph

    oen mroe question can i run a simulation of SCS united hydrograph on ( implicit & explicit to compare results of flood routing ) ?

    bcoz am doing like hydrology then hydraulics and compare each one and comment why there's a different

    sadly i got no real values of volumes in my sewers to see which is close Stuck out tongue

    and am waiting if u guys are using linear or non linear reservoir

    and please agaaaain :3when the sewer is in charge wot method u guys are using ( INSA or others ? )

    cordially .

Children
  • oen mroe question can i run a simulation of SCS united hydrograph on ( implicit & explicit to compare results of flood routing ) ?

    If you are referring to the Implicit vs. Explicit (SWMM) numerical solver - yes, you can compare results with scenarios. You can create two separate calculation options for the different solvers, then assign to a new scenario, compute each scenario separately, then compare the results. Note that the catchment runoff from the SCS Unit Hydrograph method will be the same as this is calculated independently from the hydraulic numerical solver. For more information on the differences between the solvers, see the following article in our Wiki:

    Differences between solvers: GVF-Convex vs. GVF-Rational vs. Implicit vs. Explicit (SWMM)

    sadly i got no real values of volumes in my sewers to see which is close

    Please elaborate on what you mean by "no real values of volumes". You can see volume of flow reported in the Hydraulic Reviewer.

    and am waiting if u guys are using linear or non linear reservoir

    I am not familiar with this terminology. can you provide a reference or explain more about what you are looking for? Are you referring to the catchment runoff hydrograph calculations, or something else?

    In general when using catchments in SewerGEMS, the catchment runoff hydrographs are computed separately based on the selected hydrograph method (such as the Unit Hydrograph method), rainfall runoff from the assigned storm event, and catchment parameters such as the SCS CN, Tc and area. The resulting hydrograph is then injected into the model network - for example the runoff would be directed to a catchbasin element which can be used to model surface gutter inlet capture, or you can directly discharge all the runoff into a manhole, to enter the subsurface sewer system. At that point the selected numerical solver is used to route the flow through the system and compute the hydraulic grade profiles, overflow, etc. 

    Typically in SewerGEMS you would be using either the Implicit dynamic or Explicit (SWMM) dynamic solver for hydraulic routing. These use the fully dynamic Saint Venant equations to account for momentum and other dynamic effects when calculating hydraulics in your sewer network (conduits, manholes, outfalls, etc). See further above for an article on the differences between the solvers.

    If you are looking for modeling of Inflow & Infiltration (I&I) for a sewer system that is separate from the storm drain system (meaning, the rainfall only enters the subsurface network by leaks/I&I), the RTK method is often used to take rainfall events on catchment areas and determine how much of it enters the sewer system. The SWMM solver uses a different RTK method that the Implicit, but once the I&I enters the subsurface networks, flow is routed with the dynamic solvers in the same way as flow that enters from manhole loads and catchment inflow.

    If you are new to hydraulic modeling, I recommend our Wastewater Collection System Modeling and Design book, along with the training we have available on learn.bentley.com. Additionally, there are other resources here: Learning Resource Guide for new users of Bentley SewerGEMS


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.