How to simulate one culvert insert into another culvert in HydroCAD?

[galaxy2014]

Hello,

I want to simulate the case that one small culvert inserts into one bigger culvert at its middle point, does anyone know how to do this in HydroCAD.

Thank you so much.

 

[psmart]

Do you mean a transition between different sizes? A sketch would help.

Or or perhaps a junction between two pipes? Normally the junction would occur at a catch-basin, modeled as a zero-storage pond with a culvert outlet.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Hello, thank you for your reply.

My case is in the screen shot as shown in the attachment, now I use catch-basin to simulate these two pipes, but how to connect them? The smaller pipe insert into larger pipe at its middle part and there is no junction box.

Thank you

 

[psmart]

I would use a zero-storage pond at the junction, as if there was a junction box or manhole.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Thank you for your reply, Peter.

So if we suppose there is a manhole or junction at the connection of two pipes, how we simulate them? Now we use two catch-basins: one represent 36" RCP and another one represents 72" RCP, then how we connect them in HydroCAD?

 

[psmart]

The catch basin at the junction would have a single 72" culvert outlet. The two incoming pipes would be defined in the upstream nodes where they originate.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Hello,

Please see the following 1st screen shot, I mark the dimension for the culverts, so you mean even if the length of 72" RCP is 100', I separate it into two culverts, one is 80' long and another is 20' long, then I create a catch-basin with a 72" culvert outlet (length-80'), a catch-basin with 72" culvert outlet (length-20') and a catch-basin with a 36" culvert outlet (length-150'), and let second and third catch-basin flow into first one, just like the 2nd screen shot?

1st screen shot

2nd screen shot

Thank you.

 

[psmart]

Correct. Just breakup the 100' run, placing a catch basin at the junction.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Thank you for that.

So for the Ke of 72" RCP (length-80'), what Ke should I use for entrance?

For 72" RCP (length-20') to 72" RCP (length-80'), Ke should be 0 theoretically, and for 36" RCP (length-20') to 72" RCP (length-80'), what entrance case it fit for this? "groove end w/headwall"?

Thank you.

 

[galaxy2014]

Hello,

I just create the model as the following screen shot and run it, but I get the warnnings:
warning: Pond Ex 72" RCP-length 80' Submerged Pond Ex 36" RCP-length 150' Primary device # 1 INLET by 1.47'
warning: Pond Ex 72" RCP-length 80' Exceeded Pond Ex 72" RCP-length 20' by 0.46' @ 12.34 hrs.
Do you know how to deal with this? Maybe this way does not work?

Thank you.

 

[psmart]

You have a tailwater condition that requires a tailwater-sensitive routing procedure.

Please click the warning message(s) for details and see

http://www.hydrocad.net/tailwater.htm

Regarding the Ke, use whatever value you feel is appropriate, down to the minimum of 0.01


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Hello, please see the screen shot below for my model. A 36" RCP insert into a 72" RCP, so I break up the 72" RCP into two pipes: a shorter 72" RCP and a 36" RCP insert into a longer 72"RCP.

I use "Dyn-Stor-Ind" method to run the model, and the following warning shows up, I clicked it and it said peak outflow of the pond was greater than the peak inflow. Do you know how to deal with this warning?

"Warning: Pond Ex 72" RCP-length 20' Qout>Qin may require smaller dt or Finer Routing"

Thank you.

 

[psmart]

Please click the warning for details.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Hello,

Yes, I did click the warning, and the following screen shot shows up.

I used smaller dt and increased the Finer Routing (my current dt is 0.01 and my Finer Routing = 3), the warning still existed, my peak outflow is larger than peak inflow, do you know why? Do you have some method to debug this?

Thank you.

 

[psmart]

Make sure you're using the zero-storage option. Using a small storage volume will make the model less stable.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Hello Peter,

Thank you so much. I use zero-storage and it works now.

But in our case, actually it is a pond with storage instead of a zero-storage culvert.

Just for the curiosity, do you know why the peak outflow is larger than the peak inflow of one culvert just because we add some storage for the culvert? The inflow should equal the outflow.

I want to figure out the principle of how HydroCAD works? Where I can find it? Just see the

https://www.hydrocad.net/

or the help in the HydroCAD software? I want to find how HydroCAD works, so I will know how to debug next time if another warning comes out.

In reality, if we want to adjust the peak discharge of a storm, usually the culvert with storage should be better than the culvert without storage, right? For the same amount of water flowing to the culvert, the culvert with storage can hold the water for a while and the peak flow will be lower than the culvert without storage, this is why we build SWM facilities (eg: pond) to adjust the peak discharge of the storm.

Best,

 

[psmart]

Routing through a very small volume tends to be unstable, that's why we provide the zero-storage option, which will give Qout=Qin. Otherwise you can try a smaller time step.

All calculations are documented in the Owners Manual, which is available on the web site.

If you have further questions I suggest you post your HydroCAD file or send it to HydroCAD support. Otherwise, make sure you review all the warning messages, that's always my first step when looking at a file.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[galaxy2014]

Thank you so much, Peter.

 

[galaxy2014]

Hello Peter,

The attachment is my HydroCAD file, I used "Dyn-Stor-Ind" method, dt is 0.01 and Finer Routing = 3. When you run it, there is warning for Pond Ex 72" RCP-35'.

Could you help me debug this?

Thank you.

 

[psmart]

In this case, warning 90 appears to be a reasonable result of tailwater timing and does not indicate a problem with the routing.

Make sure you set the finer routing back to 1. I also suggest a shorter time span (0-30 hours) to improve calculation speed. Your file will be more readable if you use the default node number format (2P, etc). You can put the longer text in the node description if you wish.


Peter Smart
HydroCAD Software

http://www.hydrocad.net