multi species solver with buoyant dispersion

Pierre Mathieu · May 21, 2010, 06:43

Hi,

I want to simulate the injection of helium into air in a garage, at constant temperature. I used the reactingFoam solver adding the gravity effect (rho*g) in the UEqn.

The point is that I can't see any buoyancy effects on my results : HE and air are mixing like if there was no difference of density effect between species and I don't understand why...
This effect is very important for my simulation because after a while the injection is turned down in order to observe the dispersion of helium.

Have I to modify the scalar transport equation? Is an other solver better for my case?

I've seen another way using alpha, like in the twoLiquidMixingFoam solver, but I don't know if I can adapt it to my simulation because even if I have two species to transport, I have only one phase.

Thank you in advance for your answers !

Pierre

Pierre Mathieu · May 26, 2010, 05:21

Hi,

If some of you is interested in my case, I think I found my problem :
reactingFoam resolves U equation with a constant density, so doesn't take into account variation of density in the flow due to mixing of species.
To solve this problem I am now running twoLiquidMixingFoam solver which calculates changes in density and return it to the velocity equation so that the changes of density impact on the flow.
I hope better results with this solver !

thekay · May 26, 2010, 09:07

Thank you for the update Pierre. Are your new results better?

Pierre Mathieu · May 27, 2010, 04:38

Hi Thekay,
No there not, and I don't understand why... I obtained quite the same results with both solvers.

May 21, 2010, 06:43	Searching for a multispecies solver with buoyant dispersion	#1
Pierre Mathieu New Member Join Date: Apr 2010 Posts: 5 Rep Power: 16	Hi, I want to simulate the injection of helium into air in a garage, at constant temperature. I used the reactingFoam solver adding the gravity effect (rhog) in the UEqn. The point is that I can't see any buoyancy effects on my results : HE and air are mixing like if there was no difference of density effect between species and I don't understand why... This effect is very important for my simulation because after a while the injection is turned down in order to observe the dispersion of helium. Have I to modify the scalar transport equation? Is an other solver better for my case? I've seen another way using alpha, like in the twoLiquidMixingFoam solver, but I don't know if I can adapt it to my simulation because even if I have two species to transport, I have only one phase. Thank you in advance for your answers ! Pierre Last edited by Pierre Mathieu; May 21, 2010 at 12:34.*

May 26, 2010, 05:21		#2
Pierre Mathieu New Member Join Date: Apr 2010 Posts: 5 Rep Power: 16	Hi, If some of you is interested in my case, I think I found my problem : reactingFoam resolves U equation with a constant density, so doesn't take into account variation of density in the flow due to mixing of species. To solve this problem I am now running twoLiquidMixingFoam solver which calculates changes in density and return it to the velocity equation so that the changes of density impact on the flow. I hope better results with this solver ! yvonneabs likes this.

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May 26, 2010, 09:07		#3
thekay Member Costas K Join Date: Nov 2009 Location: UK Posts: 51 Rep Power: 17	Thank you for the update Pierre. Are your new results better?

May 27, 2010, 04:38		#4
Pierre Mathieu New Member Join Date: Apr 2010 Posts: 5 Rep Power: 16	Hi Thekay, No there not, and I don't understand why... I obtained quite the same results with both solvers.