Community
Civil 3D Forum
Welcome to Autodesk’s Civil 3D Forums. Share your knowledge, ask questions, and explore popular AutoCAD Civil 3D topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Hydraflow Free Outfall Condition?

7 REPLIES 7
SOLVED
Reply
Message 1 of 8
pbradburyYWE5N
1147 Views, 7 Replies

Hydraflow Free Outfall Condition?

pbradburyYWE5N
Enthusiast
Enthusiast

Hello, 

 

I am new to using Hydraflow in Civil 3d. I previously used Bentley's StormCAD to model pipe system hydraulics. When using StormCAD there was an option to set an outfall to a free outfall condition, meaning the starting HGL was essentially at the invert of the pipe at the outfall. In my short review of the Hydraflow software I have been unable to figure out how to model this type of condition. Anyone can advise how this can be accomplished or how I could trick the software into modeling this would be greatly appreciated! 

 

Thanks very much for any help!

 

 

0 Likes

Hydraflow Free Outfall Condition?

Hello, 

 

I am new to using Hydraflow in Civil 3d. I previously used Bentley's StormCAD to model pipe system hydraulics. When using StormCAD there was an option to set an outfall to a free outfall condition, meaning the starting HGL was essentially at the invert of the pipe at the outfall. In my short review of the Hydraflow software I have been unable to figure out how to model this type of condition. Anyone can advise how this can be accomplished or how I could trick the software into modeling this would be greatly appreciated! 

 

Thanks very much for any help!

 

 

7 REPLIES 7
Message 2 of 8
fcernst
in reply to: pbradburyYWE5N

fcernst
Mentor
Mentor
Accepted solution

If you set the tailwater elevation below critical depth, it will use critical depth.

 

You can choose an elevation, crown, critical depth, normal depth  or (dc+D)/2.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com

If you set the tailwater elevation below critical depth, it will use critical depth.

 

You can choose an elevation, crown, critical depth, normal depth  or (dc+D)/2.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com
Message 3 of 8
pbradburyYWE5N
in reply to: fcernst

pbradburyYWE5N
Enthusiast
Enthusiast

This is what the help menu says regarding the min starting depth: 

 

Min. Starting Depth
Specifies how to choose the starting water surface elevation at the downstream end of any line, except outfalls. The choices are: Normal, Crown, (dc + D)/2, and Critical depth. If the starting hydraulic grade line (HGL) at any line, other than an outfall line, is below the Minimum Starting Depth, Hydraflow Storm Sewers Extension automatically sets the starting HGL to this specified depth. This value refers to all lines upstream, not the beginning HGL.
 

All of this says "except outfalls", if this setting doesn't apply to outfalls, then how does the software calc the starting HGL at the outfall? Or does this indeed apply to outfalls and the help menu is just poorly written?

0 Likes

This is what the help menu says regarding the min starting depth: 

 

Min. Starting Depth
Specifies how to choose the starting water surface elevation at the downstream end of any line, except outfalls. The choices are: Normal, Crown, (dc + D)/2, and Critical depth. If the starting hydraulic grade line (HGL) at any line, other than an outfall line, is below the Minimum Starting Depth, Hydraflow Storm Sewers Extension automatically sets the starting HGL to this specified depth. This value refers to all lines upstream, not the beginning HGL.
 

All of this says "except outfalls", if this setting doesn't apply to outfalls, then how does the software calc the starting HGL at the outfall? Or does this indeed apply to outfalls and the help menu is just poorly written?

Message 4 of 8
fcernst
in reply to: pbradburyYWE5N

fcernst
Mentor
Mentor

That setting is for the junctions... You set the tailwater elevation when you hit Run.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com
0 Likes

That setting is for the junctions... You set the tailwater elevation when you hit Run.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com
Message 5 of 8
pbradburyYWE5N
in reply to: fcernst

pbradburyYWE5N
Enthusiast
Enthusiast

Yes I see the option to set the Tailwater elevation but it is already populated by an elevation and any elevation I try to put in that is lower than the one that is in there it just reverts back to the one it has in there.. The question is, where does this elevation even come from, how does the software know to start at this elevation? Is it critical depth?

0 Likes

Yes I see the option to set the Tailwater elevation but it is already populated by an elevation and any elevation I try to put in that is lower than the one that is in there it just reverts back to the one it has in there.. The question is, where does this elevation even come from, how does the software know to start at this elevation? Is it critical depth?

Message 6 of 8
fcernst
in reply to: pbradburyYWE5N

fcernst
Mentor
Mentor

Click on the cell above that one... A little tricky there.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com
0 Likes

Click on the cell above that one... A little tricky there.



Fred Ernst, PE
C3D 2025
Ernst Engineering
www.ernstengineering.com
Message 7 of 8
lynn_zhang
in reply to: pbradburyYWE5N

lynn_zhang
Community Manager
Community Manager

Hello @pbradburyYWE5N ,

Just checking to see if your problem has been solved. Did you follow the suggestion above and did it work for you? Let us know if you still need help.





Lynn Zhang
Community Manager


0 Likes

Hello @pbradburyYWE5N ,

Just checking to see if your problem has been solved. Did you follow the suggestion above and did it work for you? Let us know if you still need help.





Lynn Zhang
Community Manager


Message 8 of 8
rmeeksRQ6VC
in reply to: lynn_zhang

rmeeksRQ6VC
Community Visitor
Community Visitor

I'm trying to figure out this issue in Hydraflow 2021. I would like to set the HGL below the critical elevation because the pond elevation at the outfall will be below critical elevation. When I set the elevation below critical in the Compute System menu, it reverts to the critical elevation when it does the calculations. Is there a way to make a keep a lower HGL elevation?

0 Likes

I'm trying to figure out this issue in Hydraflow 2021. I would like to set the HGL below the critical elevation because the pond elevation at the outfall will be below critical elevation. When I set the elevation below critical in the Compute System menu, it reverts to the critical elevation when it does the calculations. Is there a way to make a keep a lower HGL elevation?

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Rail Community


Autodesk Design & Make Report