Hydraflow HGL Issue with Box Culverts

[Anonymous]

I have encountered an odd behavior with Hydraflow when attempting to run analysis on a  box culvert running under pressure. Whenever I run the analysis, the HGL will not go above the top/crown of the box, even though the capacity of the box is clearly being exceeded. Hydraflow verifies this as you can see in the screenshot - The actual flow is 698 cfs, but the capacity is 390 cfs. However, the HGL just tracks along the crown of the box.

If I reduce the flow into the system to reach partial flow, the HGL line works fine since it's below the crown, but once the capacity of the box is reached, the HGL won't keep going up. Also, if I change the box to a circular pipe within Hydraflow, the HGL will jump up to the expected location above the pipe and for every pipe (including the box culverts) upstream of the circular pipe. The issue seems to be limited to the shape of my pipes. Does anyone have experience with this?

[Timothy_Sean_Hulbert]

Greetings,

Thank you for your recent forum post.  My name is Sean and I am more than happy to help you with this issue. I understand you have questions about the Hydraulic Grade Line generated by Autodesk Hydraflow. I will see if I can reproduce this issue in my environment. Would it be possible for you to provide the file you are working with?

I have subscribed to the thread though and will continue to monitor it should you need additional assistance. If you would like to communicate directly, you may do so at any time by sending me a private message in the forum.

[Anonymous]

Sean,
Attached is the Hydraflow file in question as requested. My issue is limited to the large box culvert in the system - You should be able to see the issue in Line 1 through Line 10 for example. I have added excess flow to the system to the point where the capacity of the box culvert is greatly exceeded, but the HGL reaches the inside top of pipe and stops. I would expect the HGL to keep rising above the pipe as it does with circular pipe. Also note that if you change one of the box culvert segments to a circular pipe, the HGL will jump up there, and continue above the pipes (circular or box) upstream.

[wfberry]

Since your file does not appear, just change the suffix of the file to .txt and there should be no problem.

Bill

[Anonymous]

Thanks for the help - Attached is my .stm file attached as a .txt file.

[fcernst]

I get the same result with your file in 2018.

..Another big problem with Hydraflow now is that it will not take a tailwater elevation above the Crown of pipe. It will go up to Crown as you have set in your file, but no higher.

It keeps setting the tailwater depth to Critical if the tailwater is higher than Crown.

Can't be used for design.

[Hidden_Brain]

Another big problem with Hydraflow now is that it will not take a tailwater elevation above the Crown of pipe. It will go up to Crown as you have set in your file, but no higher.

Thanks for the heads up! that's not good. one hydraulic software does not let water rise above pipe, another makes the water disappear when surcharged. Perfect! 

[Anonymous]

I am have exact problem with analyzing a simple three pipes network system. The HGL will not go above the top/crown of the box although the incoming inflow is way above the capacity of the pipe system. The first two pipes are connected with drop curb. The HGL in the second pipe is not going about the top/crown of the box while the HGL in the first pipe go above the crown of the box in respond to change in inflow. Any help would be appreciated! Thanks.

[wfberry]

Autodesk purchased Boss International sometime prior to 2010 and with Boss they employed its' founder Chris Maeder.  Chris left Autodesk several years ago and as far as I can tell the "Good Ship SSA" has no captain. Perhaps someone can convince me I am wrong.

Bill

[BrianHailey]

As far as I know, @Charlie.Ogden is the head of all things water in the Infrastructure team at Autodesk. Perhaps he can enlighten us on this issue.

[xiaoming.fei]

@Anonymous Thanks for your testing. I checked it in Civil 3D 2018. Followings are the results of stm file, actual flow is 615.50cfs (smaller than your flow). But results are similar, HGL line is same to rectangular pipe obvert.

From this table, we could do a simple check.

• Total pipe loss = EGLup – EGLdown = 667.65+3.68-667.61+3.68 = 0.04ft.
• Meanwhile, Total pipe loss = Sf * Length = 1.126%*9 = 0.10134 ft.

They should be same in this case, but they are different. Total pipe loss calculated by Sf is more reasonable, since actual flow is bigger than capacity flow, HGL should be higher than pipe obvert.

There probably exists a defect when calculating rectangular pipe EGLup. Need to check codes to make clear where the problem is.

I will log a defect for this.

[xiaoming.fei]

@fcernst The tailwater problem you described could be reproduced. I will also log a defect for it. Thanks!

[Anonymous]

Howdy,

I am also encountering this issue. Has there been any updates or "work arounds" found for this issue?

[timothy.lawrenceHBY8Y]

All, For HGLs capping at the top of pipe you need to change you have the analysis type set to "Kinematic Wave". Set it to "Hydrodynamic", you'll get the results you want. Input>Project Options>Link Routing Method>Hydrodynamic