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compressible, rhoSimpleFoam, multi-species, steady state, rocket nozzle

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Old   July 8, 2016, 08:27
Default compressible, rhoSimpleFoam, multi-species, steady state, rocket nozzle
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Hey fellow Foamers,

I am new to OpenFOAM, and need some clarification on a few subjects...

I am looking to use rhoSimpleFoam (or another solver) in order to solve a multispecies, compressible rocket nozzle simulation. For proprietary reasons, I cannot post much about the geometry of my nozzle. It is a nozzle designed for Ma = 2. I have cut it axially in half, due to the symmetrical nature of the nozzle. The geometry is just a supersonic diffuser (throat to outlet of a diverging nozzle). It has an inlet, walls group, outlet, and symmetry plane.

I have come up with a decent 3D mesh of 122946 cells (it's a small geometry), and it passes all checkMesh criteria. I have used the files from the constant folder of the reactingFoam tutorial in order to bring multiple species to the rhoSimpleFoam solver. I am using the combustion of methane and O2 as my reaction file, but have turned off the combustion and chemistry (don't need it - used another program). As a preliminary test, I am just running O2 through it. Later I will add the other necessary products from my particular rocket combustion.

I have attached my 0 folder if anyone wants to check it out - I'm not sure if it's right. (Sorry if it's messy with commented out lines. I've been trying a lot of things)

My problems/Questions:
  • I either get a "converged" solution of completely wrong solution, or my residuals start to decrease nicely before they increase a little, and then repeat the pattern (making a 1000 iteration wave pattern of a rise and descent of residuals) Therefore causing my solution to have a pattern of incorrect results.
  • I seem to be getting JANAF errors, telling me that I have some cells with negative temperatures (ie. T = -1500, or T = -2249). How do I solve this? I believe this is my major problem. I am getting negative pressures, extremely low temperatures, and high velocities.
  • Do I need to change the rhoSimpleFoam.C to allow for multi species?
  • Can I use sonicFoam for the same purpose? I understand it is a time-accurate solver, and I am looking for the steady state solution, but I think it might be better for my purposes. I just want to ask your opinion before I invest the time.
  • Lastly, are my BC's correct? I have no idea if that is the main reason for my poor solution.

I know that was a lot, but if I have left anything out, please let me know!
Thank you all for your time! I appreciate any suggestions!
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Old   April 18, 2017, 11:01
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enginpower is on a distinguished road
I'm curious to understand if you solved.

Me too, I'm interesting in solving a steady-state supersonic flow, but it's not clear to me how to set it to get the steady-steady solution
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compressible, multi species, rocket nozzle

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