[HarishZHAW]

Hi All,


I hope you are having a great day !


For my research, I am computing the response of laminar premixed flames to acoustic forcing. I am then changing various fuels to see the effect of different fuels on the flame dynamics.


For computing the diffusive mass and energy fluxes, I am using the Fickian model where one needs to specify the binary or mixture averaged diffusion coefficients. The binary diffusion coefficients can be extracted from literature or CHEMKIN or Cantera, where they are written down in terms of a polynomial expansion. In other words,


ln(D_ij) = A_0 + A_1 ln(T) + A_2 ln(T)^2 + ...


My question is how do I specify this in Openfoam. In the Fickian.H file the following is written: "The mixture diffusion coefficients are specified as Function2<scalar>s of pressure and temperature but independent of composition."


Please, can anyone instruct me how to use this Function2<scalar> object. More specifically, how do I instruct OpenFoam to know that D_ij will be of the above form in terms of temperature. Any suggestions would be great please.


Thanks,


Harish.

[keitaro7_14]

All you need to understand Function2 is here:


https://github.com/OpenFOAM/OpenFOAM...ions/Function2


Function2 is a template class which admit 2 arguments and return 1. The logic behind is programmed in its derived classes.


In OF case, the mixture diffusion parameters depend on that, pressure and temperature, and for that reason is a Function2.


If you have an expression for that relationship, and it only depends on the temperature, I would use the coded version.


Only you need is, in the thermophysicalTransport dictionary, introduce that relationship when you define the variable Dm, for example.


The use of coded would be something similar to this: Coded boundary condition


To begin, try to mimic other Function2 as this: https://github.com/OpenFOAM/OpenFOAM...nt/Constant2.H

[HarishZHAW]

Hi JuanMi,


Super ! Thanks a lot for your quick response.


Yes, you right, the coded function object seems to be the best option. However, I was not very confident of my coding skills and therefore, I implemented it using the table 2 function object. This is the format that I have for specifying the transport properties in the thermophysicalTransport file:


OH-H
{
type uniformTable;

low (91192.5 200.0);
high (151987.5 3000.0);

values
10 20
(
(9.376082804843815e-05 0.00025530938139315393 0.00047145082144682174 0.0007348424533524699 0.0010410077644183143 0.0013868237506628248 0.0017699361503138813 0.002188478205786576 0.002640916115086698 0.0031259559832085212 0.003642483925028823 0.004189525479741268 0.004766216970381311 0.005371784614578548 0.0060055288661967346 0.006666812404327898 0.0073550507369047535 0.008069704723696992 0.00881027453768912 0.009576294724034665 )
(8.72945640450976e-05 0.0002377018378487985 0.00043893697169186853 0.0006841636634660926 0.0009692141254929134 0.0012911807333757335 0.001647871588223269 0.002037548674353019 0.0024587839692186498 0.002910372811952761 0.0033912781370958006 0.0039005926880349736 0.004437512351734324 0.005001316710124855 0.005591354461631442 0.006207032238512181 0.006847805858497529 0.007513173363442027 0.008202669397158836 0.008915860605135722 )
(8.166265668734935e-05 0.0002223662354069405 0.0004106184573891673 0.0006400240722747318 0.0009066841819127253 0.0012078787505772988 0.0015415572922088641 0.001906093921168953 0.0023001527453980915 0.0027226068240848405 0.003172485999218652 0.0036489415468714263 0.004151221232267593 0.004678651115923251 0.005230621915719736 0.005806578545704943 0.006406011932142849 0.007028452501284476 0.007673464919922781 0.008340643791901158 )
(7.671340476690394e-05 0.0002088894938671259 0.0003857324902746723 0.0006012347345611117 0.0008517336254331662 0.0011346739778150382 0.001448129577529539 0.0017905730774617436 0.002160749548707298 0.002557600349897881 0.0029802141204781276 0.0034277935743337643 0.0038996320666756174 0.004395096502836994 0.004913614526888236 0.005454664694450098 0.0060177687847402525 0.006602485683024811 0.007208406439927461 0.007835150228755633 )
(7.232978163736657e-05 0.000196952951360433 0.0003636906336875482 0.0005668784640147624 0.000803063132551271 0.0010698354647970362 0.0013653793159564226 0.0016882546158925012 0.0020372781459240237 0.0024114517584751445 0.0028099161707365204 0.0032319196558004064 0.003676795948579868 0.004143948131246308 0.004632836553923194 0.005142969569052949 0.005673896282755095 0.006225200786851965 0.006796497500503034 0.007387427358541026 )
(6.842006371102243e-05 0.0001863068458814907 0.00034403168051524833 0.0005362363848788294 0.0007596543145755267 0.0010120065207539532 0.0012915750286074269 0.0015969976096280418 0.001927155002901104 0.002281103014773786 0.002658028810156168 0.0030572212960274115 0.003478050221629605 0.003919950934962725 0.004382412956413833 0.004864971213969007 0.005367199186389955 0.00588870344702213 0.006429119257232601 0.006988106960782053 )
(6.491134249507257e-05 0.00017675264865679886 0.00032638903023241505 0.0005087370830901715 0.000720697683058833 0.0009601087504588787 0.001225340411755764 0.0015151002963137833 0.001828326541213868 0.0021641233729905148 0.0025217196404045696 0.0029004407167439548 0.003299688671802446 0.0037189278100928412 0.004157673830443893 0.004615485510688544 0.005091958202472522 0.005586718654867148 0.006099420833784775 0.006629742501254768 )
(6.174493554409342e-05 0.000168130568234516 0.0003104676141235168 0.0004839206400126021 0.0006855416985193778 0.0009132741772657627 0.0011655677087432877 0.0014411929647862817 0.0017391398806668498 0.002058556379186099 0.0023987089262384933 0.0027589558037320544 0.0031387282487876926 0.0035375166974053853 0.003954860472861264 0.004390339876020811 0.004843569997473862 0.005314195793654117 0.005801888110185518 0.006306340428022828 )
(5.887307807692628e-05 0.00016031054180500363 0.00029602725997823694 0.00046141270326782995 0.0006536560381231277 0.0008707963085557272 0.0011113552571738324 0.0013741607338659894 0.0016582496536590894 0.001962809570851862 0.0022871410692041445 0.0026306322779770753 0.0029927408883789627 0.003372981037060949 0.0037709134741235307 0.004186138021322169 0.004618287672009962 0.005067023896274856 0.005532032849246657 0.0060130222685799055 )
(5.6256496829062894e-05 0.00015318562883589237 0.0002828704928680931 0.00044090547201148194 0.0006246046586509886 0.0008320942503976949 0.0010619616901883287 0.0013130869234719456 0.0015845496690520188 0.0018755735899251128 0.0021854903550172938 0.0025137152878447607 0.0028597301822287867 0.003223070768747129 0.0036033173197180406 0.004000087442596739 0.004413030442142852 0.004841822834218195 0.005286164722613472 0.005745776834420799 )
);
}


In the above, I have specified the binary diffusion coefficient for the species pair OH-H in terms of the two dimensional table as a function of pressure and temperature. The pressure varies along the row, while the temperature varies along the column. The low and high values signify the



Hope this helps you and all others.


Thanks and have a nice day !


Harish

[Eigen]

Hi Harish,

Can you please verify whether or not your method works as expected?