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Old   July 26, 2012, 20:37
Default Need help with transient pressure drop
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Marc Mendes
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Hi all,

Im working on modeling an intake manifold. So far ive gotten the geometry (the interior volume of air) meshed and ready to go. Ive even done a simple one cylinder pressure out with a atmospheric pressure in, simulation.

Want I want to do however is simulate the transient pressure change in all four valves through one engine cycle at different engine speeds.

Im thinking Ill have to use compressible, turbulent and transient settings to solve it. Not sure which models are best to use for this.

I was reading the user's manual on UDF's hoping I could just import my excel file of pressure drops. The programming language is way over my head though and was hoping someone could walk me through setting this up since im no computer programmer. And maybe a little help with post processing as well, later.

Im using pro/e wildfire5 and fluent14

-Marc
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Old   July 27, 2012, 02:11
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Marion
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Hi,
If you want to have pressure tables (P vs. time) you can just use the transient profiles - no udf, no compilation, no programming :-):-)
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Old   July 28, 2012, 17:03
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Marc Mendes
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So I had seen those before. But when I try to read a "profile" fluent wont recognize any files I have. What do I have to do to turn my excel/csv files into a "profile" file?

edit : I figured out how to get my tables into fluent. I have to write a text file using this (http://hpce.iitm.ac.in/website/Manua...ug/node213.htm) format.

Still not sure which models are the best to use for compressible and turbulent. Running a sim right now to see if that profile file is going to work.

Assuming it works how do I set up an animation to view the solution as a steady state picture does my very little good

Last edited by mmendes413; July 28, 2012 at 22:14.
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Old   July 30, 2012, 02:42
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Hi,
I'm glad you could figure it out. Do not forget to read your profile using file / read transient table.
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Old   July 31, 2012, 00:06
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thanks for pointing that out. Still cant get an animation to work however. Ansys is making files and storing data but any time i try to view it, nothing or very little is viewable. I can provide the workbench file if that would help anybody
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Old   July 31, 2012, 02:29
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Are you trying to open it with CFD post?

With my transient cases, I save the results (.cas and .dat files) every 5 time steps, then I open the 1st one with CFD post and it reads all the time steps automatically...

When you say "ansys is storing data" - are you telling "ansys" to save the files every ** time steps?

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Old   August 1, 2012, 18:11
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Im trying to view it within the solution window. Yes, Ive been telling ansys to save them as mpeg files. IM trying to view 3 different animations. pressure and velocity contours as well as pathlines but the pathlines never seems to work.

How do I open an animation in CFD post?
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Old   August 2, 2012, 01:39
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I meant your .cas and .dat files (the Fluent files) If the mesh doesnt change you do not need to save the .cas files, only the .dat files.
That's how I work, I am not saying it is the right way, I just find it convenient to have the Fluent files after the run so that I can do the postprocessing I want.
If you save pictures or animations and not the result files, and if you made a mistake or want to postprocess something else then you will have to run the analysis again.
For CFD post: no it doesn't open animations, it is a postprocessing software, that can open the result files you save during the run and then you can choose what animations you want to create.
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Old   August 9, 2012, 00:39
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I've been using the workbench so If the results I get are useless I well clear all the data generated in the solution and start over.

I meant that if I tell fluent to save the files as metafiles or PPM's the files are being created but are useless after the simulation as I cant actually see anything happeining.

I feel like I'm still not getting all the transient flow specifications right in the setup process.

Here's a question, when I specify time in the profile file A: do I even need to. B: should I label time as 1, 2, 3... etc? Does fluent consider anything in the time column as the "time step". For instance, when it reads the profile does it see ".00001 seconds" or in the above case does it see "time step one" and that I have to specify the correct time step in the solver to get the correct correlation between the time step and the equivalent pressure drop?

Last edited by mmendes413; August 9, 2012 at 01:18.
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