ID #1004

How to Update and Animate a Developing Steady State Simulation in CFD-VIEW?

Many users who are running steady-state simulations like to watch the results develop. Most of the time users hit the "Reload the Same Data File(s)" button again and again. You will be happy to hear that there are two easier ways to do it.

First, you can ask the solver (CFD-FASTRAN or CFD-ACE+) to write out intermediate results (say, every 50 iterations) to uniquely named files. Then you can animate those files using VIEW's file-based animation. Second, you can tell VIEW to *automatically* reload the same data file(s), using a device known as a "Trigger" file. Each of these options is described below.

Animation of Unique Iteration Stamped Files

In a CFD-ACE+ simulation, choosing the option for writing a unique DTF file at a specified interval of iterations in the Out/Output section of the CFD-ACE-GUI allows a user to output unique iteration-stamped DTF files. For example, if the steady state simulation is to be run for a total of 100 iterations and the user sets the iteration frequency to 25, DTF files will be output at the end of iterations 25 (modelname_steady.000025.DTF), 50 (modelname_steady.000050.DTF) and 75 (modelname_steady.000075.DTF) in addition to the final results at the end of the run that are stored in the file modelname.DTF.

At the end of the run, the steady state files can be animated in CFD-VIEW by using the procedure outlined in the user tip on File Based Animation with CFD-VIEW.

For a CFD-FASTRAN steady state run, unique iteration stamped files can be obtained by specifying a positive cycle value for the Cycles Interval under the Out/Output/Output Cycles/Cycles Interval field in the CFD-FASTRAN-GUI. The procedure for animating these results is the same as mentioned for the CFD-ACE+ files in the previous paragraph.

Automatic Reloading Using Trigger Files

The Trigger File update option in CFD-VIEW allows users to monitor a developing steady state solution in a running CFD-ACE+ or CFD-FASTRAN simulation. If you are interested in learning more about this feature, please read on.

Trigger File Based updating tracks a running simulation by means of tracking the modification time of a trigger file (modelname.RUN for CFD-ACE+ and modelname.TRIG for CFD-FASTRAN). The solver first generates a data set and then activates the trigger file to make CFD-VIEW aware of the new data. Each time the trigger file is changed, the solution from the data files is automatically reloaded into CFD-VIEW. This is the same as performing a manual operation of Reload the Same Data File(s) under the File menu in VIEW.

For the trigger file updating, the user should set the option for writing a DTF file at a specified interval of iterations in the Out/Output section of the CFD-ACE-GUI with the Unique File option turned off. This will ensure that the DTF file will get updated with the results at the specified iteration frequency. Since CFD-VIEW automatically reloads the same DTF file upon a trigger event, it is necessary to overwrite the DTF files with the latest results rather than write unique iteration-stamped DTF files.

For a CFD-FASTRAN simulation a DTF file can be updated with results at a specified cycle frequency by specifying a negative cycle value for the Cycles Interval under the Out/Output/Output Cycles/Cycles Interval field in the CFD-FASTRAN-GUI. For example, specifying a value of -100 for the Cycles Interval in a 1000 cycle simulation will overwrite modelname.DTF with results at the end of every 100 cycles.

To perform automatic updating using the Trigger File in CFD-VIEW, please follow the following steps in CFD-VIEW as the CFD-FASTRAN-SOLVER (or the CFD-ACE-SOLVER as the case maybe) is running.

  1. Select the Import Additional Data File... option from the File menu to load the DTF file of interest.
  2. Configure the model as desired (select variable, create cutting planes, choose color attributes, etc.) in CFD-VIEW.
  3. Click on the Select Trigger File option from the File Menu. Choose the trigger file (modelname.TRIG) from the Open Trigger File dialog. Note: The trigger file will have a *.RUN extension for a CFD-ACE+ simulation.


  4. Select the Enable Trigger option from the File Menu to turn on trigger file monitoring. From this point forward, each time the trigger file (or the RUN file for CFD-ACE+) is touched by the CFD-FASTRAN-SOLVER, CFD-VIEW will reload its data set.


  5. Please click on this link (updating using trigger files) to view an animated GIF of the pressure variable being tracked over a NACA0012 airfoil at an interval of 100 iterations over the course of 1000 CFD-FASTRAN-SOLVER iterations.

The animated gif was recorded using the procedure outlined in the tip on "File Based Animation with CFD-VIEW".

Note about Transient Simulations
Since the trigger file update option is based upon reloading the same data set during the course of the simulation, use of the trigger file is not suitable for transient simulations. This is so because the user would already be writing out unique time stamped DTF files which can be animated in VIEW to track the solution over time.

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Last update: 2012-08-07 17:00
Author: ESI-CFD Support Team
Revision: 1.7

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