[felicemastronzo]

To whom it may concern,
I'm trying to simulate fresh concrete with OF using the Herschel-Bulkley model.
I have following parameters from literature:
tau0 [Pa] a [Pa*s^b] B [-]
1804 111 1,23

so in OF (the density is 1400Kg/m^3) I will have
tau0 [Pa]/[Kg/m^3] k [Pa*s^b]/[Kg/m^3] n [-]
1,288 0,079 1,23

Correct?

But then there is another parameter nu0.

Now according to some suggestion I should set nu0 to a very high value.
Is it correct? If I have correctly understood the solver, it uses the minimum value between the provided nu0 and the value calculated according to Herschel-bulkley model as

nu=[tau0+k(gammap^n-(tau0/mu0)^n)]/gammap

Is it correct?

So if I set nu0 to 0.008, the calculated nu file in each folder appears as


/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format binary;
class volScalarField;
location "67";
object nu;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -1 0 0 0 0];
internalField uniform 0.008;

boundaryField
{
patches_name
{
type calculated;
value uniform 0.008;
}
etc.
}

I presume that nu is calculated using nu0.

If I set nu0 to 100 (high value), I get forces of a wrong order of magnitude

smoothSolver: Solving for Ux, Initial residual = 0.665612, Final residual = 2.48012e-05, No Iterations 25
smoothSolver: Solving for Uy, Initial residual = 0.559982, Final residual = 1.92865e-05, No Iterations 25
smoothSolver: Solving for Uz, Initial residual = 0.649273, Final residual = 2.05462e-05, No Iterations 25
GAMG: Solving for p, Initial residual = 0.461244, Final residual = 0.0335985, No Iterations 4
GAMG: Solving for p, Initial residual = 0.0031342, Final residual = 0.000248612, No Iterations 1
GAMG: Solving for p, Initial residual = 0.000523932, Final residual = 3.57448e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.000134293, Final residual = 8.17402e-06, No Iterations 2
GAMG: Solving for p, Initial residual = 2.77999e-05, Final residual = 2.03199e-06, No Iterations 2
GAMG: Solving for p, Initial residual = 7.14375e-06, Final residual = 5.00659e-07, No Iterations 2
time step continuity errors : sum local = 2.7234, global = 0.172896, cumulative = 0.240496
smoothSolver: Solving for epsilon, Initial residual = 0.171581, Final residual = 1.73496e-14, No Iterations 25
bounding epsilon, min: -1.11366e+06 max: 2.27262e+08 average: 1.60725e+06
smoothSolver: Solving for k, Initial residual = 0.948208, Final residual = 2.28427e-11, No Iterations 25
ExecutionTime = 53.45 s ClockTime = 54 s

forces valveForces output:
sum of forces:
pressure : (-90485.8 -1.47324e+09 1.52142e+09)
viscous : (-411.764 216421 -521637)
porous : (0 0 0)
sum of moments:
pressure : (1.18322e+08 -1.52143e+07 -1.47032e+07)
viscous : (-34016.4 5146.98 2233.21)
porous : (0 0 0)

and the calculated nu file appears like

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format binary;
class volScalarField;
location "1";
object nu;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 2 -1 0 0 0 0];

internalField nonuniform List<scalar>
1606466
([{i¾$‡ñ?S‰M‚ö?ì"î(ð?¯DÅlŒá? pÛASá?›ÿ...
etc.

I think this is because the numbers are to high... but where I'm wrong?

What in the settings should be changed?

Thanks
Franco

[araujo]

Maybe I'm wrong, but I think the force coefficients calculation is not implemented for varied nu. You have to check how OpenFOAM is calculating the coefficients in the source code. Cheers

[nimasam]

i guess you see weird number, because u save data in binary format , go to controlDict and change write format from binary to ascii to see the correct number