Wednesday, April 20, 2016

Getting Profile Output in a 2D Area

Written by Christopher Goodell, P.E., D.WRE  |  WEST Consultants 
Copyright © The RAS Solution 2016.  All rights reserved. 

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:


15 comments:

  1. Chris,

    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

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    Replies
    1. Jeremy, 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.

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    2. Hi 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

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    3. That'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.

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    4. Thanks 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.

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  2. You 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

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  3. Hi 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)

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    Replies
    1. Could be the model is unstable. What is your Courant number?

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    2. Try to reduce the computational time interval, maybe 1 min or less. What Chris said, what is your Courant number?

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    3. i have same question. how to fix this.. i mean how to stable the model.

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  4. Thanks 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

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    Replies
    1. MAX results is simply a collection of the maximums that occured during the simulation. The MAX results do not represent any given timestep.

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  5. i 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

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