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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0003480||OpenFOAM||Bug||public||2020-04-14 13:14||2020-11-04 09:47|
|Summary||0003480: Error in a fomula of the lagrangian library at /PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.C|
|Description||At line 197 to calculate the vapor concentration at surface: const scalar Cs = pSat/(RR*Ts);. Here, `Cs` is supposed to be the surface vapor concentration of component i.|
According to Raoult's law, the partial pressure of each component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multiplied by its mole fraction in the mixture. The partial vapor pressure of component i can be calculated with `ps = X[lid]*pSat`, and the corresponding vapor concentration should be `Cs = X[lid] * pSat/(RR*Ts)`.
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Just looking at the code, I agree with you. However, the code is not straightforward, and I can't be 100% sure. I need some evidence that the current implementation is wrong and that your proposal is correct. This is a commonly used model; we can't just change it on a hunch. Do you have any evidence?
It seems to me that you could prove the correct-ness of this model in the presence of multiple species by creating two cases that simulate the evaporation of a single drop (potentially in a single cell). The drop in the first case would be 100% water. The second would be 50% water and 50% some other species with identical properties to water. If the results were the same, then the handling of Raoult's law would be proven consistent. Can you construct such a test?
||I agree with you, and the proposed test case is convincing. I will try it later.|
I have carried out a test with mixed water parcel in a box, with 50% H2O and 50% anotherH2O (with the same liquid properties). The results are different though, with different particle diameter at time=0.5. This indicates that they are evaporating with different rates. I am working with OpenFOAM-6. The orig case was from the $FOAM_TUTORIALS.
waterParcelInBox.tar (1,699,840 bytes)
Thanks for confirming it.
More importantly than the evaporation rates being different, if we apply your proposed fix then the evaporation rates become the same. See the attached graphs for before and after.
This has been fixed in dev and version 8 by the following commits.
|2020-04-14 13:14||zhangxusjtu||New Issue|
|2020-04-16 11:59||will||Note Added: 0011292|
|2020-04-16 11:59||will||Note Edited: 0011292|
|2020-04-16 12:51||zhangxusjtu||Note Added: 0011294|
|2020-11-04 02:36||zhangxusjtu||File Added: waterParcelInBox.tar|
|2020-11-04 02:36||zhangxusjtu||Note Added: 0011658|
|2020-11-04 09:47||will||File Added: beforeAndAfter.png|
|2020-11-04 09:47||will||Note Added: 0011661|
|2020-11-04 09:47||will||Assigned To||=> will|
|2020-11-04 09:47||will||Status||new => resolved|
|2020-11-04 09:47||will||Resolution||open => fixed|
|2020-11-04 09:47||will||Fixed in Version||=> 8|