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October 20, 2015, 10:03 |
sprayFoam Evaporation Model
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#1 |
New Member
Mr.liu
Join Date: Sep 2012
Posts: 27
Rep Power: 13 |
HI
I am a new foamer and now i meet a problem that i can not solve, please help me if u know. i use sprayFoam in OF 2.3.0 to simulate SPRAY A (900K atmosphere), PhaseChangeModel, LiquidEvaporationBoil (default setting). The liquid should evaporate quickly because atmosphere T is 900K. However, the evaporation rate is very slow. My friend told me that, 2.3.0 sprayFoam is same as 2.0.0 dieselFoam, so i simulated it again using dieselFoam, 2.0.0, evaporationModel, standardEvaporationModel (default setting), the results seem good, evaporate and mix fast. So, i am confused that, why there is no dieselFoam in 2.3.0 and the sprayFoam can replace the dieselFoam? is there any difference in Ecaporation Model? or it just changes another name? Thanks u |
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October 21, 2015, 07:45 |
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#2 | |
New Member
Mr.liu
Join Date: Sep 2012
Posts: 27
Rep Power: 13 |
Quote:
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January 7, 2016, 07:33 |
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#3 |
Member
Join Date: Feb 2015
Posts: 31
Rep Power: 11 |
Hi,
do you solve your problems? I am having similar problems with sprayFoam since I see that, considering even the aachenBomb tutorial, the spray starts to evaporate even if both gas and liquid temperature are imposed at 300K. On my opinion this is not true. Opinions regarding this point are welcome! Stefano |
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January 7, 2016, 07:40 |
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#4 | |
New Member
Mr.liu
Join Date: Sep 2012
Posts: 27
Rep Power: 13 |
Quote:
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January 7, 2016, 07:42 |
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#5 |
Member
Join Date: Feb 2015
Posts: 31
Rep Power: 11 |
The version that I am using is the 2.3.1
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January 7, 2016, 08:01 |
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#6 |
New Member
Mr.liu
Join Date: Sep 2012
Posts: 27
Rep Power: 13 |
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January 9, 2016, 08:20 |
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#7 | |
Member
Pascal Balz
Join Date: Feb 2015
Location: Germany
Posts: 44
Rep Power: 11 |
Hi,
some time ago I had similar problems with the evaporation rate in sprayFoam. Quote:
Have a look at the source code of the liquidEvaporationBoil model: Code:
else { // evaporation // surface molar fraction - Raoult's Law const scalar Xs = X[lid]*pSat/pc; // molar ratio const scalar Xr = (Xs - Xc)/max(SMALL, 1.0 - Xs); if (Xr > 0) { // mass transfer [kg] dMassPC[lid] += pi*d*Sh*Dab*rhos*log(1.0 + Xr)*dt; } } As you can see the mass transfer is strongly dependent on the 'molar ratio' (which you might not change) and 'Dab' which basically is the vapor diffusivity and therefore a liquid property. I changed this value so that the evaporation rate fits my desired values, as I needed a completely new liquid property anyway. You can find this value in the liquidProperties source code of your specific liquid (i.e. C2H6.C). Just change the value of 'D_' there and remember to look up which polynomial interpolation is used for the specific liquid (NSRDS functions). After the changes recompile the code and it should work I don't know if there are any other possibilities to 'tune' the evaporation rate, but this worked perfectly for me.
__________________
Regards, Pascal |
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January 10, 2016, 06:08 |
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#8 |
Member
Join Date: Feb 2015
Posts: 31
Rep Power: 11 |
Hi Pascal,
thank you for your quick answer. After looking to the source code, I arrive to your considerations. So I perfectly agree with you. Thanks, Stefano |
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July 9, 2016, 15:10 |
Evaporation in SprayFoam
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#9 |
New Member
Join Date: Mar 2016
Posts: 3
Rep Power: 10 |
Hi I am MJavad
I have a question . I m solving a Water spray Injection in a Air crossflow . every thing is ok but the rate of mass transfer phase change for evaporation is not noticable . I have applied LiquidEvaporation as Evaporation Model in sprayCloud and As I told after running code I can see many parcles which should be evaporated but they are in domain yet .. Thanks If you could help me MJavad |
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