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April 24, 2016, 06:55 
natural convection in a melting furnace

#1 
New Member
donny
Join Date: Feb 2016
Posts: 3
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hey guys,
im new in openfoam. i have to simulate two gases in a melting furnance. i know i have to use the buoyantBoussinesqSimpleFoam, but i dont know how to integrate two different gases in the hotRoom tutorial. the gases are not reacting. The temperature difference accure natural convection. The Temperature of the floor is 1023 K an the ceiling 623 K. Please i need your help. regards Donny 

April 25, 2016, 03:09 

#2 
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Tobias Holzmann
Join Date: Oct 2010
Location: Leoben (Austria)
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Dear donny,
first hint, buossinesq approximation is in my opinion the wrong choice. You should take the buoyantSimpleFoam but to clear my mind just one question, why you think boussinesq is the right approach?
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Best regards, Tobias Holzmann Some interesting OpenFOAM tutorials, publications and videos on www.Holzmanncfd.de OpenFOAM Beginners should check out the new wiki on wiki.openfoam.com A list of some active OpenFOAM contributers can be found »here« A book about the basics of »Mathematics, Numerics, Derivations and OpenFOAM« can be found on www.Holzmanncfd.de 

April 25, 2016, 06:02 

#3 
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donny
Join Date: Feb 2016
Posts: 3
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Hey Tobi,
thank you for the answer. i read in another forum that this solver is the right choice for natural convection. Therefore i tried it just for one gas and it worked, but i do not know how to do it with two gases. By the way, you have a privat message from me. best regards Donny 

April 25, 2016, 14:38 

#4 
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Tobias Holzmann
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Hey guys,
I was writing via messages with donny and now I will summarize.
Code:
rho = rho1 * S + rho2 * (1S);
The easiest approach would be: implement only one passive scalar and use one fluid inside. Doing this leads to a first guess but hence we only use thermodynamics out of one gas, you will be not as accurate as in the method I mentioned above. If the thermodynamic data are very similar (cp, rho, nu, mu ...) then the passive scalar should work fine. This would be my suggestions.
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Best regards, Tobias Holzmann Some interesting OpenFOAM tutorials, publications and videos on www.Holzmanncfd.de OpenFOAM Beginners should check out the new wiki on wiki.openfoam.com A list of some active OpenFOAM contributers can be found »here« A book about the basics of »Mathematics, Numerics, Derivations and OpenFOAM« can be found on www.Holzmanncfd.de Last edited by Tobi; April 26, 2016 at 03:06. 

April 26, 2016, 07:00 

#5 
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donny
Join Date: Feb 2016
Posts: 3
Rep Power: 2 
Hey Tobi,
thank you for this helpful answer. Im now using the reactionFoam solver without reaction and only with O2 and N2. I changed all BC's and the properties for my case. I tried to run the simulation but i got this. Reading g Creating reaction model Selecting combustion model PaSR<psiChemistryCombustion> Selecting chemistry type { chemistrySolver ode; chemistryThermo psi; } Selecting thermodynamics package { type hePsiThermo; mixture reactingMixture; transport sutherland; thermo janaf; energy sensibleEnthalpy; equationOfState perfectGas; specie specie; } Selecting chemistryReader foamChemistryReader chemistryModel: Number of species = 2 and reactions = 1 Selecting ODE solver KRR4 Reading field U Reading/calculating face flux field phi Creating turbulence model. Selecting turbulence model type RASModel Selecting RAS turbulence model kEpsilon Floating point exception: 8 i dont know how to fix this problem. Under the following link you can download my case. thank you!! meltingfurnance.zip 

April 26, 2016, 08:01 

#6 
Senior Member
Tobias Holzmann
Join Date: Oct 2010
Location: Leoben (Austria)
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Hi,
maybe I will check it but as I told above, the bad thing using a reaction solver is, that it is soooo slow. Finally I am not sure if you have buoyancy included. So you have to check it yourself. My suggestion to you, build your own solver. Its so much faster, clean (you know whats going on) and really not a big deal to implement sth. like that into OpenFOAM.
__________________
Best regards, Tobias Holzmann Some interesting OpenFOAM tutorials, publications and videos on www.Holzmanncfd.de OpenFOAM Beginners should check out the new wiki on wiki.openfoam.com A list of some active OpenFOAM contributers can be found »here« A book about the basics of »Mathematics, Numerics, Derivations and OpenFOAM« can be found on www.Holzmanncfd.de 

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