[lcbuijs]

Dear Foamers,

I would like to edit buoyantBoussinesqPimpleFoam to implement temperature-dependent viscosity. I've started to work on createFields.H, by trying to output the viscosity. So far I've added:

    volScalarField nu
    (
        IOobject
        (
            "nu",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        <function goes here>
    );

However, this works only for any random name other than "nu". Can anyone point me in the right direction or tell me what steps I should take to change the viscosity?

Many thanks!
Luuk

[agustinvo]

Hi,

I think you can't do this in this way, since in this solver, nu is a transportProperties variable, and this creates a conflict between the nu the solver has and the one you define.

I propose you two thinks:

• Modify the solver and include your nuModified instead of nu
• I think there are different options to express nu as a function inside the transportProperties file... take a look to this thread

[lcbuijs]

Originally Posted by agustinvo

• Modify the solver and include your nuModified instead of nu
• I think there are different options to express nu as a function inside the transportProperties file... take a look to this thread

Heres my problem: buoyantPimpleFoam is the go-to solver for this kind of implementation. I can't get that solver to work for my geometry however, and am therefore stuck with buoyantBoussinesqPimpleFoam, which works fine so far. I haven't been able to find anything on how to modify viscosity in the main buoyantBoussinesqPimpleFoam solver.

Can anyone here show me an example on how this or something comparable is done?

Many thanks again!
Luuk

[alexeym]

Hi,

In general it is done through implementation of new viscosity model. You can find existing models in $FOAM_SRC/transportModels/incompressible/viscosityModels. So you take, for example, powerLaw model; copy it into myCoolNewViscosityModelWithTemperature; rename source files, correct Make/files and Make/options; add const volScalarField& T_ as a property of new class; use U.mesh().lookupObject("T") to initialize T_; and finally in calcNu method you utilize T_ to calculate new value of viscosity.

[lcbuijs]

Originally Posted by alexeym

Hi,

In general it is done through implementation of new viscosity model. You can find existing models in $FOAM_SRC/transportModels/incompressible/viscosityModels. So you take, for example, powerLaw model; copy it into myCoolNewViscosityModelWithTemperature; rename source files, correct Make/files and Make/options; add const volScalarField& T_ as a property of new class; use U.mesh().lookupObject("T") to initialize T_; and finally in calcNu method you utilize T_ to calculate new value of viscosity.

Dear Alexey,

Thank you very much for your reply. I'll look into this!

[alexeym]

Hi,

It turns out there is an example of implementation - http://www.tfd.chalmers.se/~hani/kur...nFoam%20v2.pdf [1]

There author decided to lookup temperature field each time calcNu is called instead of looking the field in constructor.

[1] - http://www.cfd-online.com/Forums/ope...tml#post538956

[alok1463]

Hi All,
I am simulating slurry flow. I am facing following problem during implementation of different functions of viscosity in different regions based on alpha. Expressions for the viscosity are given below.


volScalarField mueff
(
IOobject
(
"mueff",
runTime.timeName(),
mesh,
IOobject::NO_READ,
IOobject::AUTO_WRITE
),
mesh,
dimensionedScalar("mueff", dimViscosity, 0.0)
);

Definition of viscosity:
forAll(mesh.cells(), i)
{
mueff[i]= mu2.value()*(1.0 + 2.5*alpha1[i] + 10.05*Foam::sqr(alpha1[i]) + 0.00273*Foam::exp(16.6*alpha1[i]));

if ((alpha1[i] > 0.305))
{
mueff[i]=mu2.value();
}
}

Momentum equation:
fvVectorMatrix UEqn
(
fvm::ddt(rho, U) + fvm::div(phi, U)
+ MRF.DDt(rho, U)
- fvm::laplacian(rho*mu2/rho2, U)
- fvc::laplacian(rho*mueff*alpha1/rho2, US)
- fvc::laplacian(mu2*gs, US)
==
fvOptions(rho, U)
- gs*(rhos-rho2)*g
- fvm::Sp(Kdf, U)
);
UEqn.relax();
fvOptions.constrain(UEqn);


Solver is compiled successfully but it gives following error during running of test case:


DILUPBiCGStab: Solving for T, Initial residual = 1, Final residual = 7.09367e-09, No Iterations 5
DILUPBiCGStab: Solving for C, Initial residual = 0.000216836, Final residual = 6.22504e-13, No Iterations 1
THERMO: iteration 1 residual: 0
#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::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam:perator/<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 ? at ??:?
#6 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7 ? at ??:?
Floating point exception (core dumped)


Please provide me the suggestions to rectify the errors.


Thank you.