CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Pipeflow with interFoam, kOmegaSST floating point error by initial condition?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 28, 2017, 07:27
Default Pipeflow with interFoam, kOmegaSST floating point error by initial condition?
  #1
New Member
 
Oliver K
Join Date: May 2017
Posts: 15
Rep Power: 7
silencebreak is on a distinguished road
Hi all,
I'm quite new to OpenFoam and still in the learning process, so there might be a dumb mistake done but I just can't find it.

The case I'm working on is a simple Pipe with two 90 degree shifts in direction which I'm going to compute with interFoam in a k-omegaSST Model. Later on I'm going to add this case (with mergeMesh and stitchMesh) to another existing case.

The intial condition I calculated for nut and omega results always in a floating point error (huge increasing of alpha.water). So I scaled the initial calculated results for nut up and for omega down to let the simulation work. But the big problem is that I need to use the exact results for my master thesis, so I can't really work with those I think.

I used the calculation presented in the wiki:



nut=c_nu*(k/epsilon)

For my purpose exactly:
with
I=5%
u=0.22179m/s
l=0.038*dh=0.038*5=0.19
=> k= (3/2)*(0.22179*0.05)=0.000184466
=> epsilon=(0.09)*((0.000184466^(1.5)/0.19)=1.18676E-06
=> omega=0.000184466^(0.5)/0.19=0.071483201
=> nut=0.09*(0.000184466/2.16671E-06)=0.002580544

Is there anything wrong with my calculation?

The furthermore:
my y+ is around 500 therefore I use Wallfunctions
my checkMesh is:
Code:
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           306028
    faces:            885040
    internal faces:   836885
    cells:            290741
    faces per cell:   5.92254
    boundary patches: 4
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     259951
    prisms:        25807
    wedges:        0
    pyramids:      0
    tet wedges:    20
    tetrahedra:    0
    polyhedra:     4963
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            4   728
            5   403
            6   131
            7   2745
            8   772
            9   80
           10   20
           12   60
           15   24

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
            defaultFaces        0        0                        ok (empty)
                   inlet      434      467  ok (non-closed singly connected)
                  outlet      491      537  ok (non-closed singly connected)
                pipeWall    47230    48035  ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.49994 -200 -2.4982) (2.5 0.0298765 652.498)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (1.01239e-15 -5.09219e-17 -4.32734e-17) OK.
    Max cell openness = 3.25094e-16 OK.
    Max aspect ratio = 8.68508 OK.
    Minimum face area = 0.00708308. Maximum face area = 0.443196.  Face area magnitudes OK.
    Min volume = 0.00105995. Max volume = 0.112088.  Total volume = 16232.1.  Cell volumes OK.
    Mesh non-orthogonality Max: 58.1296 average: 6.74092
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 2.12244 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End
Here a Link for downloading my Case: https://www.dropbox.com/s/bmgut4sxqu...unnel.zip?dl=0

Thank you for any kind help!
silencebreak is offline   Reply With Quote

Old   June 29, 2017, 04:14
Default
  #2
Senior Member
 
Alex
Join Date: Jan 2014
Posts: 126
Rep Power: 11
Kina is on a distinguished road
I can't run your case because of version limitations.
However, I have some questions:

- your initial pressure for outlet is 995 Pa. Your internalField is 0 and inlet is zeroGradient. This results in an initially very large gradient. Try using the same value for internalField as you use for outlet, i.e. 995 Pa.
- you don't need to specify an epsilon for kOmegaSST
- nut is a function of k and omega. It doesn't make sense to fix k, omega and nut at inlet. You can leave the wallFunctions on, but set every other nut to value uniform 0 and type calculated.

Rest looks ok. Does this solve your problem?

Cheers,
Alex
Kina is offline   Reply With Quote

Old   June 30, 2017, 05:50
Default
  #3
New Member
 
Oliver K
Join Date: May 2017
Posts: 15
Rep Power: 7
silencebreak is on a distinguished road
Quote:
Originally Posted by Kina View Post
I can't run your case because of version limitations.
However, I have some questions:

- your initial pressure for outlet is 995 Pa. Your internalField is 0 and inlet is zeroGradient. This results in an initially very large gradient. Try using the same value for internalField as you use for outlet, i.e. 995 Pa.
- you don't need to specify an epsilon for kOmegaSST
- nut is a function of k and omega. It doesn't make sense to fix k, omega and nut at inlet. You can leave the wallFunctions on, but set every other nut to value uniform 0 and type calculated.

Rest looks ok. Does this solve your problem?

Cheers,
Alex
Thank you for your answer

-Yes you're completely right. I changed it-
-Yes, forgot to delete it after changing from k-epsilon to k-omega
- ok changed that too, but actually didn't solved the problem. It just runs when the omega value is e-2 in the internalField smaller than my calculated value

Yeah I'm working on OpenFoam version 2.4.0 so it's a little bit older...

I quick list my files for the 0-folder:
k
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0.000184466;

boundaryField
{
    pipeWall
    {
        type            kqRWallFunction;
        value           uniform 0.001;
    }
 inlet
    {
        type            fixedValue;
        value           uniform 0.000184466;
    }
    outlet
    {
        type            zeroGradient;
    }
    atmosphere
    {
        type            inletOutlet;
        inletValue      uniform 0.001;
        value           uniform 0.001;
    }

    defaultFaces
    {
        type            zeroGradient;
    }
}
omega
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0.0714832;//working with 0.071483201e-2


boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 0.071483201;
    }
 outlet
    {
        type            zeroGradient;
    }
    pipeWall
    {
        type            omegaWallFunction;
        value           uniform 0.071483201;
    }

    defaultFaces
    {
        type            zeroGradient;
    }
}
nut
Code:
dimensions      [0 2 -1 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    pipeWall
    {
        type            nutkRoughWallFunction;
        value           uniform 0;
        Ks              uniform 0.001;
        Cs              uniform 0.5;
    }
    inlet
    {
        type            calculated;
        value           uniform 0;
    }
    outlet
    {
        type            calculated;
        value           uniform 0;
    }
    atmosphere
    {
        type            inletOutlet;
        inletValue      uniform 0;
        value           uniform 0;
    }
    ".*"
    {
        type            calculated;
        value           uniform 0;
    }
    defaultFaces
    {
        type            zeroGradient;
    }
}
p_rgh
Code:
dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 995.21;

boundaryField
{
    pipeWall
    {
    type            zeroGradient;
//        type            fixedFluxPressure;
//        value           uniform 0;
    }

/*    Diffusor
    {
        type            zeroGradient;
//        type            fixedFluxPressure;
//        value           uniform 0;
    }
*/
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 995.21;
    }

    atmosphere
    {
        type            totalPressure;
        p0              uniform 0;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1;
        value           uniform 0;
    }

    defaultFaces
    {
        type            fixedFluxPressure;
        value           uniform 0;
    }
}
U
Code:
dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    pipeWall
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    inlet
    {
        type            fixedValue;
        value           uniform (0 0.22179 0);
    }
    outlet
    {
        type            zeroGradient;
    }
    atmosphere
    {
        type            pressureInletOutletVelocity;
        value           uniform (0 0 0);
    }
    defaultFaces
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
}
alpha.water
Code:
boundaryField
{
    defaultFaces
    {
        type            zeroGradient;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 1;
    }
    outlet
    {
        type            zeroGradient;
    }
    pipeWall
    {
        type            zeroGradient;
    }
}
Do you have or anybody else another idea why there are such problems with Omega?

Edit: Ok got it somehow to run by scaling my velocity up to 10 at the inlet. Is there any chance to get it to run with lower velocity or isn't it possible because there may be high roughness so the water is "stuck" in the pipe?

Cheers
Oli

Last edited by silencebreak; June 30, 2017 at 07:40.
silencebreak is offline   Reply With Quote

Old   July 2, 2017, 02:22
Default
  #4
Senior Member
 
Alex
Join Date: Jan 2014
Posts: 126
Rep Power: 11
Kina is on a distinguished road
Hi Oli,

I don't think the water can get stuck at the inlet.
- At which iteration does your solver crash?
- What is the error message?
- Can you get more iterations out of it by lowering the URF? (especially rho)
- Can you run the case in laminar?

Also, you say that your case blows up because of alpha. Why are you using the vanLeer Scheme for it? I'd recommend using upwind schemes for everything except (rhoPhi,U) for the start. Also try sticking to the regular schemes for grad, laplacian and snGrad at first. From my experience, those "corrections" don't make a case more stable.

Cheers,
Alex
Kina is offline   Reply With Quote

Old   July 2, 2017, 09:56
Default
  #5
New Member
 
Oliver K
Join Date: May 2017
Posts: 15
Rep Power: 7
silencebreak is on a distinguished road
Hi Alex,

Thanks a lot!

well ok


That's the error shown. So really high time step continuity errors...

-So it's the second PIMPLE-Iteration after the first overall loop
Code:
Reading g
Calculating field g.h

No finite volume options present

time step continuity errors : sum local = 2.66909e-05, global = -2.66909e-05, cumulative = -2.66909e-05
DICPCG:  Solving for pcorr, Initial residual = 1, Final residual = 26.5344, No Iterations 1001
DICPCG:  Solving for pcorr, Initial residual = 0.00866168, Final residual = 0.00224598, No Iterations 1001
DICPCG:  Solving for pcorr, Initial residual = 0.00315044, Final residual = 0.00240493, No Iterations 1001
time step continuity errors : sum local = 0.000296733, global = -1.02198e-05, cumulative = -3.69107e-05
Courant Number mean: 0.0414476 max: 0.306375

Starting time loop

Courant Number mean: 0.0414476 max: 0.306375
Interface Courant Number mean: 0 max: 0
deltaT = 0.1
Time = 0.1

PIMPLE: iteration 1
smoothSolver:  Solving for alpha.water, Initial residual = 0.00223217, Final residual = 2.81256e-13, No Iterations 2
Phase-1 volume fraction = 0.994931  Min(alpha.water) = 0  Max(alpha.water) = 1.01124
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.994931  Min(alpha.water) = -3.4422e-12  Max(alpha.water) = 1.01107
smoothSolver:  Solving for alpha.water, Initial residual = 0.00222075, Final residual = 2.77984e-13, No Iterations 2
Phase-1 volume fraction = 0.994933  Min(alpha.water) = 7.86653e-36  Max(alpha.water) = 1.02199
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.994933  Min(alpha.water) = -5.57699e-12  Max(alpha.water) = 1.02166
smoothSolver:  Solving for alpha.water, Initial residual = 0.00220966, Final residual = 2.74783e-13, No Iterations 2
Phase-1 volume fraction = 0.994935  Min(alpha.water) = 1.31058e-32  Max(alpha.water) = 1.03228
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.994935  Min(alpha.water) = -9.56679e-12  Max(alpha.water) = 1.03178
smoothSolver:  Solving for alpha.water, Initial residual = 0.00219878, Final residual = 2.71654e-13, No Iterations 2
Phase-1 volume fraction = 0.994937  Min(alpha.water) = 5.67318e-32  Max(alpha.water) = 1.04211
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.994937  Min(alpha.water) = -1.35423e-11  Max(alpha.water) = 1.04146
smoothSolver:  Solving for alpha.water, Initial residual = 0.00218807, Final residual = 2.68592e-13, No Iterations 2
Phase-1 volume fraction = 0.994939  Min(alpha.water) = 1.90742e-31  Max(alpha.water) = 1.05151
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.994939  Min(alpha.water) = -1.72803e-11  Max(alpha.water) = 1.0507
DICPCG:  Solving for p_rgh, Initial residual = 1, Final residual = 0.0479137, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 0.0236374, Final residual = 0.000948872, No Iterations 10
DICPCG:  Solving for p_rgh, Initial residual = 0.00121067, Final residual = 0.00455552, No Iterations 1001
time step continuity errors : sum local = 10.171, global = 0.178457, cumulative = 0.17842
DICPCG:  Solving for p_rgh, Initial residual = 0.3773, Final residual = 0.0186415, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 0.0134827, Final residual = 0.00214595, No Iterations 1001
DICPCG:  Solving for p_rgh, Initial residual = 0.00266194, Final residual = 0.00149583, No Iterations 1001
time step continuity errors : sum local = 4.05418, global = 0.143921, cumulative = 0.322341
PIMPLE: iteration 2
#0  Foam::error::printStack(Foam::Ostream&) in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigFpe::sigHandler(int) in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2  ? in "/lib64/libc.so.6"
#3  Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#4  Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#5  Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#7  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/bin/interFoam"
#8  Foam::fvMatrix<double>::solve() in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/bin/interFoam"
#9  ? in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/bin/interFoam"
#10  __libc_start_main in "/lib64/libc.so.6"
#11  ? in "/projects2/OF_bin/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/bin/interFoam"
Floating point exception (core dumped)
-The error message is still the Floating point exception
-Actually the opposite. The time step arises to 258.** but crashes at the same time
-Nope, still the same error at the same Iteration step

But it's absolutely not clear for me why the flow velocity affects whether it crashes or not...

For my thesis I want high accurate results but you're right better start with low order numerical schemes. But I tried with your suggestions with upwind instead of vanLeer and the standard discretization, it survived until the beginning of the third iteration but crashed anyway

Cheers
Oli
silencebreak is offline   Reply With Quote

Reply

Tags
initial conditions, interfoam

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Maximum number of iterations exceeded chtmultiregionsimpleFoam Moncef OpenFOAM Running, Solving & CFD 28 July 13, 2020 14:26
Segmentation fault when using reactingFOAM for Fluids Tommy Floessner OpenFOAM Running, Solving & CFD 4 April 22, 2018 12:30
Cannot run the code properly: very large time step continuity error crst15 OpenFOAM Running, Solving & CFD 9 December 14, 2014 18:17
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 06:20
[snappyHexMesh] determining displacement for added points CFDnewbie147 OpenFOAM Meshing & Mesh Conversion 1 October 22, 2013 09:53


All times are GMT -4. The time now is 18:14.