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melting problem: looking for appropriate solvers 

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May 17, 2013, 00:13 

#41 
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Liam Montgomery
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Hi Fabian,
Thank you for the effort which you have put into the meltFoam solver. I am interested in using your solver in the development of a thermal storage model. In your paper you indicate the choice of constants C and b in the porosity function for the meltFoam test case based on the work of Gau and Viskanta. In your own experiment, you follow the work of Shmueli et al. in guide the selection of the large constant C. I intend to model the location of the phase front in a melting Silicon body. Could you please point me in the right direction regarding the selection of the constants C and b? Brent and Voller et at. (1988) state "Further work needs to be carried out in the area of mushy region phase change to establish guiding principles in assigning appropriate values for both the constants C and b". ...I am hoping there has been some development in this area since 1988! 

May 17, 2013, 03:15 

#42 
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Fabian Roesler
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Hi Liam
Unfortunately, there are not much more references I can recommend to you. Shmueli et al. performed a parametric study on the large constant C. However, they modeled a VOF gas phase above the melt. This may lead to wrong results. In my present study I found out, that the large constant is not the only parameter to vary. Next to the permeability (which is the large constant C), the viscosity of the melt in the transition region has to be taken into account. Moreover, by using the liquid fraction as porosity function, porosity is changing linear. This is not necessarily the case for all PCM. As you use a pure PCM (silicon) you should choose a large C for the Darcy source term. You could also use the switchof technique instead of the Darcy term. Soon I will publish a paper on all this stuff concerning the Darcy type source term. Also keep in mind that my solver is for nonisothermal phase change of mixtures. Regards Fabian 

May 27, 2013, 10:59 

#43 
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Liam Montgomery
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Hi Fabian,
Thanks for getting back to me on this. Your advice has been helpful so far  I'll be sure to share my findings with you. Just to keep you in the loop, I also emailed Vaughan Voller with a similar question and this was his response: With a pure material where one would physically expect a sharp interface between the solid and liquid the choice of the parameters in the porosity model are not criticalprovided they are sufficient to "switch of" the liquid velocity in the computational cell undergoing the phase change So in a first case I would use the Gallium melting values. But there would no harm in seeing what happens when you adjust these valuesI would not expect adjustment up to 1/2 and order to have much impactbut worth and easy to check. Thanks again for your help. Liam Montgomery 

May 27, 2013, 11:11 
Parametric study for Darcy cosntant

#44 
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Fabian Roesler
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Hi Liam
Thanks that you share your knew findings with us. Vaughan Voller is for sure wright when he says, that the C has no big impact when it comes to isothermal melting. A higher C does not change much. Is C to low, you will see your solid PCM sinking downwards. I would suggest a parametric study varying C from a low value lime 100 to say 10e8. This will give you a feeling. Apropos, when you use different densities for solid and liquid, C will become more and more important. Regards and thanks again for the discussion Fabian 

June 5, 2013, 16:02 
Thanks for all your contributions!

#45 
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einat
Join Date: Jul 2012
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I just downloaded the erfMelt piece and the meltFOAM piece. Will try to use this to model lava!
anyone has any kind of documentation for these? no worries if not. Just figured it will save me some time if someone already wrote something. 

June 5, 2013, 16:05 

#46 
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einat
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I just downloaded the erfMelt piece and the meltFOAM piece. Will try to use this to model lava!
anyone has any kind of documentation for these? no worries if not. Just figured it will save me some time if someone already wrote something. 

June 11, 2013, 08:53 
No documentation jet

#47 
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Fabian Roesler
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Hi
I did not write any documentation for the solver, since it is not 100 percent finished. The erfMeltSolver reduces the nonlinearity effects in the energy conservation equation. However, it does not entirely get rid of it. For simple problems, the results converge with a very small error for the energy conservation. With increasing convective transport, the error increases and some iteration to account for the nonlinearity have to be performed. F. Rösler, D. Brüggemann (2011): Shellandtube type latent heat thermal energy storage: numerical analysis and comparison with experiments. Heat and Mass Transfer, Vol. 47 Issue 8 , 10271033, DOI: 10.1007/s0023101108669 http://www.springerlink.com/content/b1tp01k2u7q8j432/ In my previous work, I use a linear liquid fraction function and the linear source method proposed by Voller. Regards Fabian 

June 11, 2013, 09:38 

#48  
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Tobias Holzmann
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Quote:
if I have time I ll rebuild the solver for OpenFOAM2.2.x At the Moment I rebuild the flamelet solver and build a transient solver for combustion based on the flamelet thermodynamic model. After that (and please write me a message if I dont Keep you updated ) I try to rebuild the solver for 2.2.x Tobi 

July 15, 2013, 23:25 
problem with liquid fraction

#49  
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Mohammad Shakil Ahmmed
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Hi,
I'm working with the meltIcoFoam solver which is basically cloned from the meltFoam. In my cases, I have seen the liquid fraction at the boundary gives some unusual value. Is there anyone who has worked with the same code of meltFoam? It will be great if anyone can upload validated case for me for the meltFoam. Cheers! Quote:


July 16, 2013, 02:03 

#50 
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Anja Miehe
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Hello Mohammad,
could you post your solver and test case? Without more information, helping you is a difficult task. Regards, Anja 

July 16, 2013, 02:47 
melting problem

#51 
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Mohammad Shakil Ahmmed
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The solver I'm using is exactly the meltIcoFoam "http://www.cfdonline.com/Forums/openfoam/93620meltingproblem.html", and the test case is as attached.


July 16, 2013, 03:28 

#52 
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Anja Miehe
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Hello Mohammad,
I do not see anything in your set up for the test case that might force the solver to crash. As I do not know, how you changed the solver to work with a newer version of OpenFOAM than 1.4 (which I guess is the one posted in #2 of this thread) I can only guess.
Regards, Anja 

July 17, 2013, 04:34 
boundary condition of liquid fraction

#53 
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Fabian Roesler
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Hi
I did not see any boundary condition for the liquid fraction in your test case. It should be zeroGradient everywhere except for inlets. Check the erfMeltFoamSolver in the thread. You do not necessarily need the boundary condition as the liquid fraction (alpha) is a function of temperature but then it has to be handled a little bit different in the solver code. All fields depending on the liquid fraction, so basically all thermo physical properties, should use the boundary condition of the liquid fraction. Code:
volScalarField xyz ( IOobject ( "xyz", runTime.timeName(), mesh, IOobject::NO_READ, IOobject::AUTO_WRITE ), alpha*x*y*z, alpha.boundaryField().types() ); Fabian 

July 17, 2013, 07:19 

#54 
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Anja Miehe
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Hello Fabian,
thanks for the reply. Again, I learned something new. Regards, Anja 

July 28, 2013, 23:51 
Temperature and liquid fraction update with Voller method

#55 
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Mohammad Shakil Ahmmed
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Hi,
Has anyone already implemented the linear source method proposed by Voller ? Will it be possible to post code for that (Just the iteration loop between temperature and liquid fraction)? Cheers shakil 

July 29, 2013, 02:43 
flT update cycle

#56 
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Anja Miehe
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Hello Shakil,
here is the frame of the way I do it. For the hEqn.h file, it is: Code:
int iter=0; double diff=0.0; do { fl.storePrevIter(); iter++; fvScalarMatrix hEqn ( ... ); hEqn.relax(); hEqn.solve(); fvScalarMatrix flEqn ( or what way you want to calculate fl out of T ); flEqn.relax(); OR fl.relax(); depending on the way of calculation as well flEqn.solve(); // if flEqn in a fvScalarMatrix is used diff = Foam::gMax(mag(fl.internalField()fl.prevIter().internalField())); }while ((iter < iterMax) && (diff1 > convergence)); The additional solving parameters iterMax and convergence are declared as follows in a file like readAdditional.h. Code:
dictionary flUpdate = mesh.solutionDict().subDict("flUpdate"); scalar iterMax = flUpdate.lookupOrDefault("iterMax", 100); doubleScalar convergence = flUpdate.lookupOrDefault("convergence", 1e6); Code:
flUpdate { iterMax 150; convergence 1e8; } Have a nice day, Regards, Anja Last edited by AnjaMiehe; July 29, 2013 at 04:04. Reason: Forgot a part 

August 6, 2013, 09:43 

#57 
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Liam Montgomery
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Hi Fabian,
I'm back onto using your solver to model a melting problem. Essentially I am trying to model the melting of a converging prism, with a heat flux applied to the top (eg: http://imgur.com/RPsaWHa) The melting occurs as expected in the xz plane with convection visibly effecting the melting front as shown here: http://imgur.com/iEl6kfu However, since your solver only appears to work in 2D (one of the assumptions in shellandtube paper), the melting is not correctly modelled in the xy plane: http://imgur.com/9J6bAbM How much effort would be involved in extending the solver to 3D if at all possible? Would I be better off using 2D results and trying to extrapolate to 3D? Thanks again for your help. Kind regards, Liam Montgomery 

August 6, 2013, 09:54 
3D melting problem

#58 
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Fabian Roesler
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Hi
the solver is fully capable of solving 3D cases . The assumption in the paper is only stated to reduce cell number and so the calculation time. However, I have to state again, that the energy conservation in my error function solver is only valid for small time steps as one would actually need an iterative correction procedure like Voller is using it. Regards Fabian 

August 6, 2013, 10:12 

#59 
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Liam Montgomery
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Ok, thanks  that's great news. Do you have any suggestions as to why convection is not appearing the same in both the xz and xy planes as shown in the images?


August 22, 2013, 04:17 

#60 
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Thomas Vossel
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Hi everyone!
I'm going to enter the fray of writing a melting/solidification solver too... That's why I'd like to ask for some headsup on the solver for OF2.1 which Fabian kindly shared with us. I understand that it's based upon the enthalpyporosity technique by Voller et al and the fluid flow is modelled using a PIMPLE solution. I'd like to ask though what general idea the simulation of the flow is based upon. Is it a VOF approach, an EulerEuler approach or even something different? 

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