[ArminAlavi]

Hello Foamers
I have problems using the moving mesh option in the pyrolysis model provided in fireFoam solver. I set up a 2D case as you see in the first picture. the red region is fluid region and the blue one is the solid region that is to be pyrolised. The red region has a very high temperature and causes the solid material to pyrolyse. Note that the case works fine without the moving mesh option in the pyrolysis model.
I have two problems here:
1.the first one is that my simulation corrupts after some iterations (i only get 0.4 seconds of simulation) and leaves me the bellow error:

--> FOAM FATAL ERROR:
Negative initial temperature T0: -0.162420488345

From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const) const [with Thermo = Foam::hConstThermo<Foam::rhoConst<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::rho Const<Foam::specie> >, Foam::sensibleEnthalpy>]
in file /home/ubuntu/OpenFOAM/OpenFOAM-6/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 54.

FOAM aborting

#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::error::abort() at ??:?
#2 Foam::heSolidThermo<Foam::solidReactionThermo, Foam::SpecieMixture<Foam::reactingMixture<Foam::co nstIsoSolidTransport<Foam::species::thermo<Foam::h ConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > > >::calculate() at ??:?
#3 Foam::heSolidThermo<Foam::solidReactionThermo, Foam::SpecieMixture<Foam::reactingMixture<Foam::co nstIsoSolidTransport<Foam::species::thermo<Foam::h ConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > > >::correct() at ??:?
#4 Foam::regionModels:yrolysisModels::reactingOneDi m::evolveRegion() at ??:?
#5 Foam::regionModels:yrolysisModels:yrolysisMode lCollection::evolve() at ??:?
#6 ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/fireFoam"
#7 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#8 ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/fireFoam"
Aborted (core dumped)

2. In the following link : https://openfoamwiki.net/index.php/FireFoam#Pyrolysis
It is suggested that if you use the moving mesh option the pyrolysis region gets smaller due to mass loss, but mine gets bigger and it is extremely irrational. as you see in the second picture, boundary cells between fluid and solid are stretched in the pyrolysis direction.
I want the solid cells that are pyrolysed completely to join the fluid region, untill all the solid region is pyrolysed and i have nothing left but a full fluid region. Is that even possible?
Thank you very much, any help would be highly appreciated.

Armin Alavi

[Kummi]

Hello Armin Alavi,
Have you coupled any solvers to find the interaction between solid and fluid regions ? - possibly multiregionFOAM and fireFOAM.

May I know what kind of interface boundary condition you have implied for energy transfer. Is there any significant purpose of using moving mesh in your case ?
I couldn't able to exactly figure out the change in second picture, where you mentioned pyrolysis zone gets bigger ?

I want the solid cells that are pyrolysed completely to join the fluid region, untill all the solid region is pyrolysed and i have nothing left but a full fluid region. Is that even possible?

If solid gets pyrolysed, let's say wood or coal, the residual char is formed as solid followed by release of volatile gases, gasification, combustion follows. I couldn't able to understand that how the solid will be completely pyrolysed into fluid.

Quite keen to know your problem objective and application.
Thank you