[Elix1D]

Hello Foamers,

Nice to meet you all!
I'm relatively new to OpenFoam and CFD in general, but for my master thesis i need to simulate a two-phase turbulent flow (the definitive version will be a tri-phase) with lagrangian computation of the particles and eulerian for the gas phase.
The solver uses a PIMPLE with maxCo = 5; Deltat = 1e-4 and adjustableTime = yes.
For now it is all cold, T = const = 300K, U(inlet) = 1 m/s.

I've checked the mesh 5 times and it does not give any errors or warnings, but when i try to run the case this is what i get (i'll cut the log because it is over 4e6 lines long):


--> FOAM Warning :
From function janafThermo<EquationOfState>::limit(const scalar T) const
in file /home/eli/OpenFOAM/OpenFOAM-2.3.x/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 108
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = -22610.8388896

//goes on and on with this warning giving out crazy temperatures ad then:


DICPCG: Solving for p, Initial residual = 1, Final residual = 0.0324826439634, No Iterations 1001
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = -4.93526606616e+13, global = 1.94990071052e+12, cumulative = 1.7857962019e+12
rho max/min : 9.61833220491e+98 -2.81232367419e+100
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam:ICPreconditioner::calcReciprocalD(Foam::Fie ld<double>&, Foam::lduMatrix const&) at ??:?
#4 Foam:ICPreconditioner:ICPreconditioner(Foam::l duMatrix::solver const&, Foam::dictionary const&) at ??:?
#5 Foam::lduMatrix:reconditioner::addsymMatrixConst ructorToTable<Foam:ICPreconditioner>::New(Foam:: lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#6 Foam::lduMatrix:reconditioner::New(Foam::lduMatr ix::solver const&, Foam::dictionary const&) at ??:?
#7 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#8 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#9 Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#10
at ??:?
#11 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#12
at ??:?

I can't post the solver because it's not mine (to have an idea: it is a derivate of fireFoam), but i'll give you all the files present in 0 folder and the fvSchemes and fvSolution, plus the shortened log file.

I've checked the boundary conditions and they seems normal to me, so i can't find where is the problem. I hope that somebody here could help me, thank you all in advance for your patience and collaboration.

Good afternoon

Elix​

[alexeym]

Hi,

As the error happens on the first time step, did you try to reduce initial time step? Now it's 0.00014367816092, can you start with something around 1e-6?

[Elix1D]

Hi Alexeym,

Thanks for your reply and suggestion.
I've tried to use 1e-6, but it gives the same error as using 1e-4.

I have re-uploaded the files from 0, fvSolution/Schemes, blockMeshDict and Error log, hopefully they won't be damaged this time.

If you find something unusual please tell me.

Thanks again for your patience and help.

Good night

Elix

[alexeym]

Hi,

sorry but it's rather difficult to say what's wrong (except that simulation is diverging) without additional knowledge about the problem you're trying to solve and additional details on solver. Do you have a case you're able to run with this solver?

[Elix1D]

Hi,

I understand and i'm sorry for not being able to post the solver, i'll try to give additional information.
This solver is currently under development to be able to simulate a fully functional hybrid rocket.

For now i'm trying to simulate the film stripping of water when subjected to an oxidant flow (i've attached a sketch of the situation) until the water is all gone (there is a region extruded over the water bowl, that can't be seen on Paraview, to apply the moving mesh).
The flow is assumed turbulent with a k-epsilon model (later we would like to use a k-omega sst), the gas flow is followed with an eulerian approach and the particles that detach from the water surface are followed with a lagrangian approach.
The interaction of gas and particle is neglected, there are no chemical reactions, all components are at constant temperature, there is no combustion and the gas flow is injected at 1 m/s.
The case should give as output: T, U, rho, p, k, epsilon, YDefault and p_rgh of the gas flow and some property of the particles such as diameter, desired diameter...

I've got a functioning case, from which i've copied the values of the properties, but the mesh is different.
The things that changed from the original case are the mesh and some of the faces names, which i've reported in the new case boundary conditions. And i've checked them countless times, so i really can't understand where lies the problem.

I hope to have given enough information, if not please tell me and i'll try to be more specific.

Thanks again for your patience and collaboration.


Have a nice day


Elix

[alexeym]

Well,

post checkMesh output to check if your new mesh is OK.

[Elix1D]

Hi,

Here i've attached the output of BlockMesh, topoSet, extrudeToRegionMesh and checkMesh. I hope they will be useful.


Thanks again for the help

[alexeym]

Hi,

meshes seem to be OK. As the error is in diverging pressure (look at the initial residuals)

DICPCG:  Solving for p, Initial residual = 0.148484454859, Final residual = 2.53300679501e-05, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 4.16053729367e-08, global = 1.62322291314e-08, cumulative = 6.05291749453e-08
rho max/min : 1.24225632205 0.867425641005
DICPCG:  Solving for p, Initial residual = 0.074025575532, Final residual = 1.57757345243e-05, No Iterations 4
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.52823355351e-07, global = 6.35896279308e-08, cumulative = 1.24118802876e-07
rho max/min : 1.12458745159 0.473585647507
DICPCG:  Solving for p, Initial residual = 0.0625867352311, Final residual = 1.83728094227e-05, No Iterations 4
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.8877978904e-07, global = -1.21803964337e-07, cumulative = 2.31483853886e-09
rho max/min : 2.33149869349 0.678279179749
DICPCG:  Solving for p, Initial residual = 0.120724812283, Final residual = 9.2807087629e-05, No Iterations 3
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 5.34819729548e-06, global = 2.1168701463e-06, cumulative = 2.11918498484e-06
rho max/min : 1.72973957191 -4.04265992618

and I don't have any idea about what the solver is solving (what's really causing divergence in pressure), there not much I can suggest.

[Elix1D]

Hi,

thanks againg for the help, i'll try to get more information from the author of the solver (he's not very collaborative).

Thanks again and good afternoon


Elix

[Elix1D]

Hi,

I've finally been able to speak with the creator of the solver, the error wasn't in the BCs files but the mesh was too much refined for a RANS solution, so increasing the number of outer correctors resolved the issue.

Thanks again for your patience and help.