
[Sponsors] 
September 6, 2013, 05:03 

#41  
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Quote:


September 6, 2013, 05:17 

#42  
New Member
sasan
Join Date: Sep 2013
Posts: 28
Rep Power: 5 
Quote:
i have a another question... is this solver useFull for condensation? or if i use for condensation,i should modify that? 

September 6, 2013, 05:27 

#43 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
yes, you should perform some (minor) modifications because we created solver only for evaporation and source term is considered to be always negative. But as I think it does not matter  evaporation or condensation  for numerical model.


September 6, 2013, 06:06 

#44  
New Member
sasan
Join Date: Sep 2013
Posts: 28
Rep Power: 5 
Quote:
do you have test case for youre solver?I will be grateful if you can provide me the test case... 

September 6, 2013, 09:38 

#45 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 

September 6, 2013, 09:45 

#46 
New Member
sasan
Join Date: Sep 2013
Posts: 28
Rep Power: 5 

September 6, 2013, 20:50 

#47 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Something like that =) We validated it earlier but now there are some problems with reproducing the results (because validating were performed by student, not by me directly)


September 7, 2013, 16:19 

#48  
New Member
sasan
Join Date: Sep 2013
Posts: 28
Rep Power: 5 
Quote:
Do you modify youre solver for 2D case?can I have modifid solver?or guide me how correct this solver... Regards, 

September 11, 2013, 16:24 

#49 
Member
Anastasios
Join Date: Mar 2009
Posts: 33
Rep Power: 10 
Dear nimasam
I would also like to have a look at your final code (a few years later than the other users of the forum/evapPhaseChangeFoam) if this is possible i would be really grateful . Thank you very much in advance Ageorg email: anastasios.georgoulas@gmail.com 

October 15, 2013, 08:24 

#50  
New Member
sara zand
Join Date: Oct 2013
Posts: 1
Rep Power: 0 
Quote:
could you please send me your code and accessories. this is my mail: sara65.zand@gmail.com thank you Mr sam;I so need it; 

October 15, 2013, 13:25 

#51 
New Member
Jose
Join Date: Oct 2012
Posts: 6
Rep Power: 6 
Hi Nima,
I would really appreciate if you could send me your code and accessories as well. My email is: llido1_2@hotmail.com many thanks in advance, José. 

December 17, 2013, 05:34 

#52 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Hello!
Above I wrote about a code developed sometimes ago (see my posts #29 and #31). In our test case I find an error: actually we did not include evaporation heat source in energy equation (but I wonder that the results of numerical computations were close to the experimental one). I cannot explain why is this. "Turning on" the source term lead to bad temperature field although the energy equation (with evaporation heat term) is right. Unfortunately I am not engaged in this problem for now and attach our test case of evaporating drop for persons interested in. It should work but sometimes the problems with convergence may arise. P.S. I forget to mention: during creation of the code we disable dimensions checking. So find and set to zero: Code:
dimensionSet 0; 

March 27, 2014, 06:21 

#53 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Hello everyone!
Long long time ago I posted about our experience in drop evaporation problem (see my posts #29 and #31). But as I studied out later an error with source term was in the energy equation. But now it seems that I found solution for the problem The idea is: instead of using simple L*Y term in energy equation one should use next energy equation fvScalarMatrix TEqn ( rhoC*fvm::ddt(T) + rhoC*fvm::div(phi, T)  fvm::laplacian(K , T) + L*Y*rhoC/(rho2*C2+alpha1*(rho1*C1rho2*C2)) ); So the factor rhoC/(rho2*C2+alpha1*(rho1*C1rho2*C2)) is appeared. If anyone is interested why is this I will write explanation and derivation of the formula (the idea is quite simple). I have tested (preliminary) solver for the problem of drop evaporation with "new" energy equation and have obtained quite good results. Update: unfortunately, this is not solved problem completely. The root of the problem is in overestimated value of source term in energy equation due to "smearing" of phase interface. Last edited by sahas; March 27, 2014 at 12:13. 

April 4, 2014, 06:05 
New Energy Equation

#54 
New Member
Join Date: Jan 2014
Posts: 13
Rep Power: 5 
Hello Alexander,
I'm very interested by your model, I am trying to simulate the condensation process which is quite close to evaporation. I'm so interested to know the reason of the addition of your ratio. I suppose that it is a correction of the latent heat term? I would really appreciate if you could send to me some documentation. Thank you very much, Miki 

April 4, 2014, 08:19 

#55 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Hello, Miki!
The modification of the source term L*Y in energy equation is obtained by the following simple model. Let us consider close volume in which the interphase front is (this will be a cell of computational grid). During evaporation (or condensation) the following equality should have place on the interphase front: , there  heat flux in liquid and gas,  mass flux of the evaporated steam,  latent heat. So, generated heat (due to evaporation) should warm both liquid and gas. Let be a volume of the cell,  volume concentration of the liquid in the cell. So during some period the liquid and gas in the cell will be warmed as follows: , Here  temperature increase in liquid and gas (in the cell),  heat capacity,  density,  square of evaporation. Quantity is unknown. For its determination let us suppose that . So: Hence , where . Another possible model, for example, if we suppose that all heat released will warm only liquid (so ). In this case simple term L*Y is appeared. As I understand, in VOF such evaporation model should be applied only in one cell of liquidgas interface. Presently I do not know exactly how to do it. 

April 7, 2014, 16:43 

#56 
New Member
Joseph Levi Dobmeier
Join Date: May 2011
Posts: 1
Rep Power: 0 
Alexander,
First of all thank you very much for posting your code and continuing to develop this thread. I am also interested in this work and am attempting to port your code to 2.3.0. A suggestion to reduce the interface smearing that you are experiencing would be to increase the cAlpha term in the fvSolution PIMPLE subdictionary (I notice you currently use a value of 1). Since OpenFOAM uses the Weller scheme for interface compression, cAlpha determines the magnitude of the artificial velocity. Rusche's thesis section 4.2.1 discusses it and gives some references. Joe Last edited by cypherpunk01; April 9, 2014 at 16:13. 

April 8, 2014, 04:17 

#57 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Joseph, thank you very much for the reference and suggestion! Increasing of the cAlpha may improve the situation but I think that if interface smears greater than one cell the problem will not be solved completely. So, the decision may be in considering socalled level function (which is distance from phase interface to given point). Or I think one needs a reformulation of evaporation energy source term like it is done with surface tension in momentum equation...


November 15, 2014, 17:40 
Error in the the surface species mass fraction determination

#58 
New Member
Monssif
Join Date: Mar 2014
Posts: 5
Rep Power: 5 
Hello,
First, thank you Mr. Alexander for sharing the solver, and giving useful explanations. I think there is an error in species mass fraction equation in the alphaEqn.H ( evapEnterFoam solver) , there is no pressure field! so I think that : volScalarField YSAT( 18.0*YSAT2/(18.0*YSAT2+29.0*(1.0YSAT2)) ); should be : volScalarField YSAT( 18.0*YSAT2/(18.0*YSAT2+29.0*(PYSAT2)) ); As I released this is Yan and Soong expression for species fraction! I think also, that the saturated vapor pressure derived from Antoine equation should be multiplied by 133.23 instead of 0.00132! so it would be in Pa (Kg/(m*s²)). Can you, please, explain what you mean by div_n_k2, and what model have you used for the source term in energy equation. is it m'*Latent heat ? Can you please send me some useful documentation or work papers for modeling evaporation with the VOF method? Thank you so much. 

November 16, 2014, 13:38 

#59 
Member
Alexander
Join Date: Mar 2009
Posts: 42
Rep Power: 10 
Hello, Monssif!
Concerning YSAT: it is the mass fraction of evaporated vapour whereas YSAT2 is the molar fraction that can be calculated as (saturation pressure)/(atmosphere pressure). So the formula is correct. Antoine equation for water vapour is correct  it is in mm Hg, 0.00132 is 1/(760 mm Hg). div_n_k2 is not more than absolute value of div_n_k (I do not remember about coefficient 0.5). div_n_k is div(n) or simple curvature in another words. > what model have you used for the source term in energy equation. is it m'*Latent heat I wrote about model in details above, please read. As for now the model for heat equation is not correct due to overestimated heat source (for details see my previous posts). 

January 21, 2015, 03:49 

#60 
New Member
WeiYang
Join Date: Jan 2014
Location: China
Posts: 3
Rep Power: 5 
Dear nimasam:
I need to simulate droplet evaporation in OF but I could not find any solver for that. From this forum I found that you have developed your own code. Is it for May I have the final version?thank you very much! my Email: yangwei@tju.edu.cn Best Wishes! Yang 2015121 

Tags 
boiling, evaporation, interfoam, phase change 
Thread Tools  
Display Modes  

