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Conjugate heat transfer and reactingFoam (chtMultiRegionReactingFoam)

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Old   August 29, 2016, 21:19
Default Conjugate heat transfer and reactingFoam (chtMultiRegionReactingFoam)
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Eric Daymo
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Hello,

If anyone is interested in a solver with conjugate heat transfer + gas phase reaction capabilities, I've posted to github a hybrid of chtMultiRegionFoam and reactingFoam called chtMultiRegionReactingFoam. Steady state and transient solvers for OpenFOAM 4 and the current OpenFOAM-dev version are available (along with tutorials) at:

https://github.com/TonkomoLLC

I hope this is useful for your work. Feel free to contact me if you have any questions or comments.

Best regards,

Eric D.
Tonkomo, LLC
Twitter: @TonkomoLLC,
email: info at tonkomo.com
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Old   August 30, 2016, 11:15
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Arvind Jay
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I was waiting for this feature. I will test and report.
-Jay
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Old   February 27, 2017, 10:57
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Mohamed el Abbassi
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Hi Eric,

Thank you for your contribution. I have studied the solver (OpenFOAM 3) this month and benchmarked the implementation of reaction in the cht-version against rhoReactingFoam which is also based on p_rgh. So only 1 region and no conjugate heat transfer. As a test case I modelled the Sandia D flame with 2-step reaction mechanism of Westbrook and Dryer.

With the steady state version I initially couldn't get ignition. Even after adjusting the relaxation factors and setting the initial internal field temperature to 2000 K. The maximum temperature immediately drops to inlet values. I found out that the convention with the SIMPLE algorithm to use a timestep of 1 s was the issue. Unlike the navier stokes equations for steady state problems, the energy and species equations are largely dependent on time, which is probably taken from the 'virtual' timestep. Choosing high timesteps allows little energy release. By adjusting the time step to a much lower value (so that max Courant nr is about 0.2), reaction was finally possible.

Attached you'll find a plot of the temperature progression along the rotation axis. Maximum temperature and temperature rise are similar, but reaction starts a little bit more upstream with chtMultiRegionSimpleFoam. Still, it is a very good result.

The transient version of the solver is less robust. I needed 4 nOuterCorrectors instead of 1 with rhoReactingFoam to get the simulation going, leading to 4 times longer runtime. Can it be due to the pimple algorithm that is implemented differently?

Best,
Mohamed
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Old   February 27, 2017, 16:57
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Eric Daymo
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Hi, Mohamed,

Thank you very much for such a detailed review of chtMultiRegionReactingFoam! This is great feedback, especially on your solution technique for the steady state solver and the benchmark findings.

rhoReactingFoam and chtMultiRegionReactingFoam (directly based on chtMultiRegionFoam for the PIMPLE algorithm) do indeed have different formulations for PEqn, but I do know know offhand if this the root cause of the nOuterCorrectors issue you are report. I am happy to look at your test cases in more detail if you wish to send them to me. To start with, I would want to repeat with OpenFOAM 4.x or OpenFOAM-dev. The OpenFOAM 3.x version you are using is a "beta" version of the chtMultiRegionReactingFoam solver and it was not as thoroughly tested as the versions on github.

I also note that since my initial August 2016 post I have placed on our github site two new solvers: "multiRegionReactingFoam" and "multiRegionReactingPimpleCentralFoam" (the latter based on https://github.com/unicfdlab/hybridCentralSolvers). I have tested multiRegionReactingFoam more extensively against reactingFoam and I would be very curious to know if this solver meets your expectations.

I look forward to further feedback. Thank you again for your insightful reply.

Best regards,

Eric
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Old   March 1, 2017, 10:10
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Mohamed el Abbassi
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Thanks for the clarity! That explains certain bugs I encountered in your beta version. I should have updated to OF 4 sooner, but it was good training exercise for me to be honest.

I will send you the case files for chtMultiRegionReactingFoam and rhoReactingFoam. Thank you very much for your effort! I will also run them again on OF 4.

The reason I used the p_rgh based solvers was because I wanted to make a consistent comparison and wasn't aware of the psi based multiRegionReactingFoam. Thanks for uploading it!

I'll keep you updated.
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