July 15, 2024
Virtual Flume
Ven Te Chow’s book “Open Channel Hydraulics” is arguably the gold-standard book for hydraulic engineers-especially those of us who model open channel flow.
Getting Profile Output in a 2D Area
Back in September 2015, I wrote an article on how to extractflow data from a transect in a 2D area. This was a round-about way of getting flow flux data out of RAS Mapper. Back then the beta version of HEC-RAS 5.0 was somewhat limited in the ways data could be extracted from a 2D area. In the final release of Version5.0, you may have noticed in the bottom left-hand corner of RASMapper, there is a very unassuming tab called “Profiles Lines”.
Profile Lines are another way of extracting linear data from a 2D area, only these are extracted longitudinally, like a profile plot. Here’s how it works:
1. Run your project and then open up RAS Mapper. Activate your results by checking either the Depth, Velocity, or WSE output layer. Turning on the particle tracing might help guide where you place your profile line.
2. Select the Profile Lines tab. Click the “+” button to draw a new profile line on your 2D area. Double click to end the line and when prompted, give it a name. Here I’ve named it “Profile 1” and it is stored in the Profile Lines bin.
3. Now select the pointer from the toolbar at the top and then right-click anywhere on your profile line. Whatever results layers you have checked in the layer manager will be available as profile plots.
4. Click on whichever value you would like to see for the profile plot. Here we can the see water surface elevation profile. Notice that the terrain is included on this plot for reference.
And the velocity profile:
And the depth profile:
Comments
Jeremy Payne
on April 21, 2016Chris,
Thanks for the article! I have two questions. First, if I'm modeling an entire stream reach with a 2D mesh, are profile lines the best way to approximate cross sections within the mesh to view results? Second, is there a way to insert monitoring points or stations for model calibration? Thanks so much for the help.
-Jeremy
Chris Goodell
on April 21, 2016Jeremy, to get "cross section" like data, you might try using a 2D area Connection. You'll only get flow and average stage at the 2D connection, but if that's all you need, it would be a good method to use. Check this out: http://hecrasmodel.blogspot.com/2015/09/transect-for-extracting-flow-in-2d-area.html
The only way I know of inserting monitoring points is by using a shapefile and bringing that in as a map layer. You can then compare your results in RAS Mapper with what you have in the shapefile.
Anonymous
on April 22, 2016You can use Crayfish to load your results and there is a Plot tool to generate plots and cross sections:
http://www.lutraconsulting.co.uk/products/crayfish/wiki
https://youtu.be/_56trD689Sk
cgarner
on October 19, 2016Hi Chris,
I would like to see the flow in my calibration for each output time step along a cross section at an internal point in my 2d mesh. Similar to Jeremy's question above. I tried using a profile line but I am getting an out of memory exception. See screen shot here:
https://www.dropbox.com/s/1df26iqs6lbbk5g/Screen%20Shot%202016-10-19%20at%209.43.22%20AM.png?dl=0
Task manager shows shows RAM usage < 8gb and my machine has 40gb. I am running 5.0.3. Does anyone have suggestions as to why this isn't working?
Thanks
Chris Goodell
on October 19, 2016That's strange. I would try the following to resolve this. 1. Close RAS. 2. Delete all of your hdf files (both plan and geometry hdf files) as well as your rasmapper file. 3. Reopen RAS. 4. Save your geometry. 5. rerun the project. 6. Try reading off the profile line again. If that doesn't fix it, try some different profile lines. See if they work or if none of them work. You can always try rebooting your machine as well, but doubt that will fix it. Good luck.
cgarner
on October 19, 2016Thanks Chris. I will try your suggestion and see if that resolves the problem. I am able to plot the depth, WSE, and velocity under Profile Line>Plots, the error only occurs under Profile Line>Time Series>Flow/Accumulated Flow. My project is a 5 day simulation with 15-minute inflows and 10 sec computational interval, and 15-minute output so maybe it is a memory issue.
Unknown
on July 6, 2017Hi Chris
I have been using HECRAS 2D and for one particular project I'm getting unusually high WSE, depths and elevations when I set the results to MAX. I'm running a 24hr simulation with 10minute intervals.
The maximum discharge is 4.3m3/s (hydrograph calculated from HECHMS)
Chris Goodell
on July 7, 2017Could be the model is unstable. What is your Courant number?
Anonymous
on October 26, 2017Try to reduce the computational time interval, maybe 1 min or less. What Chris said, what is your Courant number?
Boniface Kinnear
on October 29, 2017Thanks for that. That approach worked although my models ran for 22 hours.
One other thing I needed clarification on with the 'MAX' results matter is what do they actually represent:
1. Are they associated with any particular time step?
2. Do they show the maximum build up of runoff in the 2D area without accounting for simultaneous emptying of the area? I normally use Normal Depth for my downstream condition, does this have any effect on how the magnitude of the maximum values, particularly the depth?
Whenever possible/suitable I also run a 1D model which doesn't always give satisfactory results in dense urban catchments without fine-tuning
regards
Chris Goodell
on October 30, 2017MAX results is simply a collection of the maximums that occured during the simulation. The MAX results do not represent any given timestep.
Unknown
on November 8, 2017i have a question. it is i have modelled the 2d area using mesh. peak values of inflow hydrographs are about 10m3/s.but i got the as peak flow of the outflow hydrograph 100000m3/s. there is some instability. how to fix this problem.. can u reply as soon as possible
Ayesh Gunathilaka
on November 8, 2017i have same question. how to fix this.. i mean how to stable the model.
Chris Goodell
on November 10, 2017Check your Courant number.
Chris Goodell
on November 10, 2017It should be close to a value of 1.
Sumiran Mathur
on February 3, 2018time series>> volume accumulation and time series>> flow both commands are giving error.
i,m running precipitation only simulation at 2 hour interval.
Can anyone please help!!
error — " unhandled exception has occurred in a component in your application…… Object refrence not set to an instance of an object"
Help !!
Anonymous
on September 19, 2018Hi Chris:
i have a problem with flow input. i want to input the flow rate along the upstrem BC line, but it appeals in the RAS mapper only the tip of the BC lien, can you please help me?
Unknown
on November 16, 2018cgarner, did this solution work for you? I am encountering the same issue.
Unknown
on December 5, 2018Hi Chris,
Can we build a model of dense river network from HecRAS2d itself as for the same we need to enter multiple internal hydro-graph as internal boundary conditions for flow conserve. Since after giving internal hydro graph there are instances of back water affect from that cell.
Mark Snyder
on August 31, 2020How were you able to plot the WSE and the terrain in the profiles? My profile is only showing the water level.
Thanks,
MArk
Chris Goodell
on August 31, 2020Is your terrain layer turned on? I think as long as the terrain layer and water surface layers are “checked”, they should both show up on that plot.
Jay
on November 11, 2020Hi Everyone,
Quick question: When creating a profile line and then clicking on the Time Series->Flow, Volume, or Rating. I am getting “Writing Post-Process File” message, that is taking a long time, is this normal?
Flow Data: precipitation over a 4.4 sq mi catchment, with mesh grid size of 100ft by 100ft. 6-hr interval for 72 hours (HMR59).
Computation Settings: Computation Interval 1 sec, mapping output interval 1 sec, hydrograph output interval 1 min, detailed output interval 1 min.
Computation only took about 1, trying to figure out why the post-process file is taking longer than the model computations. Is this normal? is anyone else having the same experience as I am?
Thanks
Chris Goodell
on November 11, 2020That seems awfully long. But if the profile line is very long, cells are small, simulation time window is long, and mapping output is small, I suppose it could take a long time to post-process.
Jay
on November 11, 2020*Computation only took about 1hr
Heels
on February 23, 2021Hi All,
Is it possible to extract time-series results for multiple profile lines all at once (i.e. instead of right-clicking each line and doing it one by one). For example, if I wanted flow data, would it be possible to have the data tabulated in columns: Time Step, Feature Line 1 Flow, Feature Line 2 Flow, and so on.
Thanks!
Chris Goodell
on February 23, 2021I don’t think that’s available in the current version of RAS. But you could always copy and past the table data from each line into Excel and then seem them all together there.
Saif
on March 2, 2021I tried it in my model, but I am getting negative flow rate; velocity and depth profiles are all ok. What could be the reason
Chris Goodell
on March 4, 2021It’s all based on the direction you draw your profile line. Left to right looking downstream should give you positive flow.
Madeline
on March 5, 2021Hi everyone,
I am curious about extracting flow across profile lines. I understand the mapper extracts flow across cell faces along the line. Is the flow reported across a cell face normal to the face? In other words, if you have a profile line that lined up exactly with cell faces, would the flow across the profile line be perpendicular to the line?
Thanks!
Chris Goodell
on March 9, 2021Madeline, I’m not 100% sure about this, but I believe the flow through a face that is reported is simply the volume of water that crossed that face over the time step. So not necessarily a normalized component to the flow in the event that the face is “skewed” to the direction of flow.
Brad
on March 6, 2021Running v5.0.7 2D with diffusion wave. 5-second computation timestep. Takes 4.5 hours to run model (3 day duration for a dam break scenario). Created 120-ft long profile line that crosses six 20-ft cells of a downstream channel. Mapping output interval 30 seconds. Hydrograph and detail intervals at 5 minutes each. Takes 8 hours to finish the “Writing post-process file” message. Double the time it took for the simulation itself. ???
Chris Goodell
on March 9, 2021That’s brutal Brad! Here’s a long shot, but by chance do you have “floodplain Mapping” checked with a bunch of stored maps? That could certainly slow down the post-processing. Also, running over a VPN or on a network drive can really slow down the post-process. Getting it on your local drive would help (if you haven’t already tried that). Not sure what else to suggest off-hand.
Brad
on March 14, 2021Thanks Chris. No – floodplain mapping is NOT checked and I am running it on a local hard drive (SSD), not over a network. So strange.
I had to extend the simulation to run an additional two days…model run was 8 hours. THEN, doing the same short profile line took 57 hours to write the post-process file before anything could be plotted. Yes – 57 hours. Crazy.
Chris Goodell
on March 23, 2021That seems very strange. How big was the resulting plan hdf file? This sounds like something HEC should hear about. Might I suggest trying in 6.0 beta2 and if it still takes that long, sending the model (via debug report under File menu item) to HEC? I’m sure they do not intend a model like yours to take 57 hours to post process!
Lorenzo Scopetani
on August 27, 2021Good morning
it’s possibile to extract the energy depth profile from the ras mapper in a 2D model?
Chris Goodell
on August 27, 2021Yes. That is one of the available maps in Version 6.0. Just bring in the energy map, then draw your profile line where you want it.
Nahuel Villarroel
on October 8, 2021Hi Chris, thank you for all your videos, it was very helpful to improve my model skills.
I Want to ask if it’s possible to obtain velocity direction or velocity components in 2d models?. I spend a long time looking for it. I want to accomplish some raster operations to apply the Mayer Petter Muller sediment transport method.
Chris Goodell
on October 8, 2021Hello Nahuel- You can get the velocity x and y components in the output hdf file, using an HDF Viewer. The path to the velocity x and y is /Results/Unsteady/Output/Output Blocks/Base Output/Unsteady Time Series/2D Flow Areas/[name of 2D area]/
Steve Zhao
on November 10, 2021Hi, Chris, what’s the difference between a profile line and a reference line? How to utilize them appropriately?
Chris Goodell
on November 11, 2021A profile line is only for viewing output. A reference line can display output results, but can also be used as a reference for Rules scripting and can also be used to set initial conditions (I think). Check out this episode of Full Momentum for more information on this: https://www.youtube.com/watch?v=YAdnv0wyepU&list=PLk_n8Ox5nf3HWWifRSMqdqBMawoJ1rV3g&index=3
Jose Suarez
on March 8, 2022Hello,
Is it possible to plot WSE and/or depth profiles within a culvert (eg crossing through a dam) in a 2D model? Or any way to get those values? RAS Mapper gives me only terrain values in those cases.
Thanks in advance.
Chris Goodell
on March 10, 2022To my knowledge, that is not available in the current version of RAS. Hopefully they’ll add that in soon!
Add Your Comment