How to change air density to zero
 

Hi, all

I'm very new about OpenFoam. I followed the damBreak tutorial and
set flow outwards, and flow inwards. Now i wanted to change the air density to zero. But the system show error.
Could anyone tell me how can I change the density to zero ?
Thanks in advance.
English is not my native language; please excuse typing errors.

hi lin,

you could try to switch the equationOfState of thermoType in thermophysicalProperties
to constant rho and then specify rho as 0.

How to change air density to zero
 

Hi, janibo
thanks for your suggestions.
I tried to add the thermophysicalProperties file, and also modified the nOuterCorrectors and nNonOrthogonalCorrectprs in PIMPLE, but there were still errors. I don't know what went wrong.


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0


PIMPLE: No convergence criteria found


PIMPLE: No corrector convergence criteria found
Calculations will do 2 corrections


PIMPLE: Operating solver in transient mode with 2 outer correctors


Reading field p_rgh

Reading field U

Reading/calculating face flux field phi

Reading transportProperties

Selecting incompressible transport model Newtonian
Selecting incompressible transport model Newtonian
#0 Foam::error::printStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::operator/<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<doub le, Foam::fvPatchField, Foam::volMesh> > const&, Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) at ??:?
#5 Foam::incompressibleTwoPhaseMixture::calcNu() at ??:?
#6 Foam::incompressibleTwoPhaseMixture::incompressibl eTwoPhaseMixture(Foam::GeometricField<Foam::Vector <double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&) at ??:?
#7 Foam::immiscibleIncompressibleTwoPhaseMixture::imm iscibleIncompressibleTwoPhaseMixture(Foam::Geometr icField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&) at ??:?
#8 ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/interFoam"
#9 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#10 ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/interFoam"
浮點數例外 (核心已傾印)


Could anyone tell me what I miss.
I have attached all the case files at below

I think you have a division by zero error while calculating nu.
Does the case work if you have rho=1e-10 or some other value?

A fluid with ρ=0 does not exist. You cannot calculate a flow of it.

From a momentum perspective, as far as the water (rho = 1000) is concerned, the difference between air (rho ~ 1) and a vacuum (rho = 0) is negligible (ignoring the fact that the water would boil). So, as has been said above, just substitute a low density gas like hydrogen for the air and it will behave like a vacuum.