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invalid solutions in reactingFoam1.7.1

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Old   December 2, 2010, 03:44
Unhappy invalid solutions in reactingFoam1.7.1
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Farshad
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Hi,
I solved my problem of janaf error by using proper boundaryconditions. Now, the problem is the solution which is almost 1655 and it does not have any variations. I tried to compile by both unit lewis number and nonunit and i also tried to use 100% O2 for my oxidiser instead of 23% O2 and 77% N2 ,but still the problem is not solved.
Please help me guess what might be the source of this problem.
Kind Regards,
farshad
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Old   December 2, 2010, 07:39
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Hi,
What are your BC? Also at what Co no did you ran your case?
Could you also give some details of your case as to what exactly are you simulating?
What reaction mechanism are you using? Are you sure that combustion is taking place?

I don't know much but I am also struggling with reactingFOAM. If you come across something then do share it here.
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Old   December 2, 2010, 10:36
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Dear Nakul,
My case is exactly the case i sent you 2 or 3 days ago. My courant is 0.1.
I am simulating a high temperature burner inside a furnace and my air speed is 86m/s and my methane speed is 75 m/s and it is a mild combustion. I also tried ignition but it doesnt change. I also compiled by unit lewis number and didnt make any difference. I still have some hope because some people say reactingFoam is a good solver.
I even used 100% O2 instead of air and still it doesnt burn i guess although the temperature increases 300 degrees but it is uniform accross the flowfield. What do you recommend about CMIX?
Thanks so much.
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Old   December 3, 2010, 02:33
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Hi,

If you would go through the source code you will find that Cmix value is to be specified by the user in case of turbulent reaction. I haven't thought much about its variation on the results. But now that you have brough it up I would try to fine out its effect. Uptil now I have been using the default value of 0.1 for the reaction.

Have you done a cold flow simulation? If not do that and check whether you are getting satisfactory results or not. For cold flow Cmix is taken as 1.

Meanwhile I would also try to find out the effect of Cmix. I am also struggling with reactingFOAM, and I also don't know much. So If you come across anything please do share it here.
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Old   December 3, 2010, 11:32
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Dear Nakul,
Thanks, I did coldflow simulation and the result were very bad. Oxygen is everywhere 1 and the methane is just very near the inlet. I think the boundary conditions that you told me has some problems. Please help me.
Is is possible to send your case? In this way i can see your discritizations schemes as well as many other parameters.
Thanks for sharing
Farshad
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Old   December 4, 2010, 04:44
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Hi,

Actually my case is on supersonic combustion so my fvSchemes and fvSolution files are very different from those available in reactingFoam tutorial. Even my BC are also quite different.

At inlet I am giving fixedValue for everything but at the outlet I am using inletOutlet fot U and T. For p its waveTransmissive. I am also facing lot of problems with my case. I am not getting accurate results but my case is running and convergence is being achieved.

As far as your case is concerned have you tries totalPressure BC at inlet for air. Also take a look at your Initial Conditions and thermodynamic properties.

If possible, upload the case setup you used for cold flow simulation. I will have a look, if I find time (my exams have begun) and see if I can find something.
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Old   December 8, 2010, 09:43
Default -37 janaf error
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Dear Nakul,
Finally i did coldflow simulation successfuly but when i start reactions after some steps that it goes really fine upto 3400 degree ,it suddenly falls in to -30 degree janaf error and...
My courant number is tested for both 0.1 and 0.09 but the results dont change. I wonder why it reaches -30 suddenly.
my initial conditions for reaction is obtained by coldflow simulation.
Thanks
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Old   December 8, 2010, 16:22
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Hi,
You may refer to the following links and see if they give you any hints.

Do not spend your time (look at the posts in the end)

dieselFoam --> Janaf Error, what are the root causes? (dieselfoam is reactingfoam only)

You may upload your mesh details and I would have a look. Beyond this frankly I also don't have any idea. I am also stuck with this problem.

As of now only thing I can say is that approach is quite correct. Taking cold flow results as initial condition is a correct thing to do.

If by reading the above posts you come up with something, do post it here.

Do tell me about any further problems you may face (they'll help me too)
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Old   May 18, 2011, 09:17
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Hi Farshad,

Even I am having problems with reactingFoam, even for cold flow simulations. What boundary conditions did you use?

Many thanks,
gk
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Old   May 21, 2011, 01:44
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Hello,

I attached my last modification for boundary conditions. I hope it is useful for you.

Kind Regards,

Farshad
Attached Files
File Type: gz dallyHM1.tar.gz (4.9 KB, 25 views)
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Old   May 24, 2011, 12:15
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Thanks so much, Farshad!
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