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Found 5 results

  1. We often get asked about instability troubleshooting and how to have a basic review of model health. Below is a short workflow for how we normally start checking mo dels, typically for instabilities but also for schematisation problems or general health. The below is for basic 2D models but also applies to 1D/2D models. How do you go about checking for instabilities? What do you find most helpful when it comes to picking up problems? Is there anything on your wishlist that your Tuflow simulation could tell you about how to get to the bottom of these? Check the Tuflow log file (.tlf) Search for the words WARNING, CHECK and ERROR in the tlf. If there are messages that you don't understand, then use the wiki messages page to help you look for what the codes means and suggestions for how to solve them What's are the cell size and time step? Is the time step around half or one quarter of the cell size (or down to one eighth for direct rainfall models)? Is the cell size appropriate for the results that you expect (ie: no depths much larger than the cell size) Scroll to the bottom of the tlf and check the simulation summary – image one below shows two examples on how to read the summary in your tlf Has the model finished? Are there any negative depths? If so, import the layer into your GIS package to find out where these instabilities are occurring. What is the peak mass balance in the model? As a rule-of-thumb this should be between ±1%. Look at your messages layer If it goes unstable, is it in the 1D or 2D? Find the first UNSTABLE errors that occur and visualise those in your GIS package, along with you model inputs, are there any correlations? Topography o Load your zpt_check file (or DEM_Z check) and review the topography around your area of interest. If you’re using topographic modifiers, also load you zsh_zpt_check file to review what changes you’re making. Are there any sharp edges or quick changes? 4. Materials o Load your grd_check file and thematically map by material or load your DEM_M to look at your materials. Are there any big changes in roughness? 5. Results o Step through the depth results and velocity vectors, look for sudden changes o Check for circulations or oscillations, particularly around boundaries. Are there circular flow paths or undulating water surface levels?
  2. Hello I have an ISIS-TUFLOW model with ESTRY channels that link to TUFLOW (but not ISIS). When the model becomes unstable in the ESTRY component the ISIS run does seem to acknowledge that the TUFLOW component is no longer valid and it just sits while ISIS continues. CTRL+C will not terminate the TUFLOW component and formally closing from ISIS is not reliably an option. The general outcome being that final results files may not generated in the ESTRY TUFLOW component making trouble shooting more difficult. When running a batch this also means that the next run cannot start without manual intervention. Can this be addressed? Thanks, Ellie
  3. Hi admins, Have just been running a ~ 50ha ROG model, pure 2D domain with the GPU solver. We really wanted to run it using 1m cells so we could pick up on small overland flow paths within the site. the model continued to be unstable until we adopted 4m cells. The 4 hour simulation ran very very fast, in about 5 minutes. Am I right in thinking that maybe the time step may have some impact on the instability? Are there any codes that can applied to slow the time step and accept (force) a smaller grid, such as a 1m or even 2m? Cheers
  4. trying to run a pure 2D model with some steep terrain, 1:1, using QT and HQ boundaries. As expected we are getting high instabilities at this change in elevation. typically we could overcome this using rainfall on grid, however in this instance, the client prefers hydrograph. has anyone modelled steep terrain with QT and HQ boundaries? can anyone suggest a method to override, overcome these instabilities?
  5. Hello I have created a modified version of an existing 1D Estry/2D Tuflow model. 1D consists of a main channel 1.8km and a 2D covers 1.2 long x 0.5km high (2.5m grid) Instability problems occurs very early in the a 100yr run (generally 20mins). When I look at the error messages, the instabilities do not make sense. For one thing, the instabilities are occuring well away from the flooding extents determined using previous simulations of the existing model. They are also located far away from the 1d channels and their boundaries (about 1.0km away). Attached in a image describes my problems further. Regards, sloan1411 Unstable.bmp
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