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Virtual-iCFD May 1, 2011 10:54

interDyMFoam deltaT drops non-stop
 
Hi everyone,

Below is my setup for controlDict to run interDyMFoam.

My concern is now (after 10 iterations) the deltaT is in the order of e-05 and continue to drops. I have tried to tighten pcorr to 1e-12 and with Gauss upwind for convection and also try Gauss linear limited 0.7 for laplacian. Also, decrease underelaxation for k and epsilon to 0.5. Still does not see the light. In this case, I also do the checkMesh and all look okay as indicated below. My PISO setting for Courant no. is also provided below. Considered this stage, my concern is time is not marching any way due to extremely small deltaT.

Any suggestion will be greatly appreciated.

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application interDyMFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 0.1;

deltaT 0.005;

writeControl adjustableRunTime;

writeInterval 0.01;

purgeWrite 0;

writeFormat ascii;

writePrecision 12;

writeCompression uncompressed;

timeFormat general;

timePrecision 10;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 0.5;
maxAlphaCo 0.5;
maxDeltaT 0.005;

libs
(
"libincompressibleRASModels.so"
"libfvMotionSolvers.so"
"libforces.so"
);

// ************************************************** *********************** //

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

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 599829
faces: 1728840
internal faces: 1677599
cells: 565109
boundary patches: 6
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 556015
prisms: 629
wedges: 0
pyramids: 0
tet wedges: 20
tetrahedra: 0
polyhedra: 8445

Checking topology...
Boundary definition 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
sidewall 16384 16770 ok (non-closed singly connected)
inlet 4096 4225 ok (non-closed singly connected)
outlet 4096 4225 ok (non-closed singly connected)
floor 8192 8385 ok (non-closed singly connected)
ceiling 8192 8385 ok (non-closed singly connected)
floatingObject 10281 11433 ok (closed singly connected)

Checking geometry...
Overall domain bounding box (-2 -1.5 -2) (4 2 2)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (2.96151165684e-16 4.64197183787e-17 9.36902725343e-15) OK.
Max cell openness = 2.53757529159e-16 OK.
Max aspect ratio = 4.49379234381 OK.
Minumum face area = 2.09352045e-05. Maximum face area = 0.00341828125. Face area magnitudes OK.
Min volume = 4.3804331189e-07. Max volume = 0.0001602417. Total volume = 83.9563743795. Cell volumes OK.
Mesh non-orthogonality Max: 51.5433563696 average: 3.4337367223
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.44827063315 OK.

Mesh OK.

End


#------------

PISO
{
momentumPredictor no;
nCorrectors 3;
nNonOrthogonalCorrectors 2;
nAlphaCorr 1;
nAlphaSubCycles 3;
cAlpha 1;
correctPhi yes;
}

Virtual-iCFD May 1, 2011 11:00

sorry, I thought I should also post the progress of the simulation too. now is dropping to e-6.

Interface Courant Number mean: 3.57569768064e-05 max: 0.347384454161
Courant Number mean: 0.00346227188823 max: 1.05310016844
deltaT = 1.11396410976e-05
Time = 0.006390756284

Centre of mass: (0.499906589644 0.24999904487 -1.20104643514)
Linear velocity: (-0.627710873661 -0.0852525959485 -26.4966964046)
Angular velocity: (-12.8920948858 -833.985757923 0.00690366308419)
GAMG: Solving for cellDisplacementx, Initial residual = 0.0551572903235, Final residual = 8.88849915274e-06, No Iterations 3
GAMG: Solving for cellDisplacementy, Initial residual = 0.0385918438553, Final residual = 3.13337111456e-06, No Iterations 4
GAMGPCG: Solving for pcorr, Initial residual = 0.0250926042783, Final residual = 4.94159179989e-07, No Iterations 7
GAMG: Solving for cellDisplacementz, Initial residual = 0.0460431089478, Final residual = 3.81392093508e-06, No Iterations 4
Execution time for mesh.update() = 12.13 s
time step continuity errors : sum local = 2.5407120133e-11, global = 3.00220714219e-12, cumulative = 2.86158988517e-07
GAMGPCG: Solving for pcorr, Initial residual = 0.00341457758679, Final residual = 7.82092422324e-07, No Iterations 4
time step continuity errors : sum local = 5.13383490686e-17, global = 6.06255486822e-18, cumulative = 2.86158988523e-07
MULES: Solving for alpha1
Liquid phase volume fraction = 0.189772205184 Min(alpha1) = -1.18791754256e-07 Max(alpha1) = 0.999999999995
MULES: Solving for alpha1
Liquid phase volume fraction = 0.18976775217 Min(alpha1) = -6.93200240088e-07 Max(alpha1) = 0.999999999995
MULES: Solving for alpha1
Liquid phase volume fraction = 0.189763302103 Min(alpha1) = -1.54970255717e-08 Max(alpha1) = 0.999999999995
GAMGPCG: Solving for pcorr, Initial residual = 1, Final residual = 9.03507236794e-07, No Iterations 7
GAMG: Solving for p_rgh, Initial residual = 0.00890734579531, Final residual = 7.26500211696e-05, No Iterations 6
GAMGPCG: Solving for pcorr, Initial residual = 0.0250926042783, Final residual = 4.94159179989e-07, No Iterations 7
GAMG: Solving for p_rgh, Initial residual = 0.00105150500514, Final residual = 8.00369639837e-06, No Iterations 4
GAMG: Solving for p_rgh, Initial residual = 0.00017536985361, Final residual = 7.89000651154e-07, No Iterations 5
time step continuity errors : sum local = 4.97052999835e-09, global = 5.82771123844e-10, cumulative = 2.86741759647e-07
GAMGPCG: Solving for pcorr, Initial residual = 0.00341457758679, Final residual = 7.82092422324e-07, No Iterations 4
time step continuity errors : sum local = 5.13383490686e-17, global = 6.06255486822e-18, cumulative = 2.86158988523e-07
GAMG: Solving for p_rgh, Initial residual = 0.000409536855082, Final residual = 2.87332492538e-06, No Iterations 4
GAMG: Solving for p_rgh, Initial residual = 0.000139728476782, Final residual = 8.59664788755e-07, No Iterations 3
MULES: Solving for alpha1
Liquid phase volume fraction = 0.189772205184 Min(alpha1) = -1.18791754256e-07 Max(alpha1) = 0.999999999995
MULES: Solving for alpha1
GAMG: Solving for p_rgh, Initial residual = 7.45188594154e-05, Final residual = 4.79430381896e-07, No Iterations 3
Liquid phase volume fraction = 0.18976775217 Min(alpha1) = -6.93200240088e-07 Max(alpha1) = 0.999999999995
time step continuity errors : sum local = 2.98207714667e-09, global = -2.88815783222e-10, cumulative = 2.86452943864e-07
MULES: Solving for alpha1
Liquid phase volume fraction = 0.189763302103 Min(alpha1) = -1.54970255717e-08 Max(alpha1) = 0.999999999995
GAMG: Solving for p_rgh, Initial residual = 7.61552247514e-05, Final residual = 4.57831986712e-07, No Iterations 3
GAMG: Solving for p_rgh, Initial residual = 6.13199105298e-05, Final residual = 3.69433582136e-07, No Iterations 3
GAMG: Solving for p_rgh, Initial residual = 0.00890734579531, Final residual = 7.26500211696e-05, No Iterations 6
GAMG: Solving for p_rgh, Initial residual = 0.00105150500514, Final residual = 8.00369639837e-06, No Iterations 4
GAMGPCG: Solving for p_rgh, Initial residual = 5.91885010226e-05, Final residual = 4.4902425514e-09, No Iterations 3
time step continuity errors : sum local = 2.79184843811e-11, global = -1.68961681819e-13, cumulative = 2.86452774902e-07
GAMG: Solving for p_rgh, Initial residual = 0.00017536985361, Final residual = 7.89000651154e-07, No Iterations 5
DILUPBiCG: Solving for epsilon, Initial residual = 0.0153215890859, Final residual = 7.67678370387e-11, No Iterations 4
time step continuity errors : sum local = 4.97052999835e-09, global = 5.82771123844e-10, cumulative = 2.86741759647e-07
DILUPBiCG: Solving for k, Initial residual = 0.039579350528, Final residual = 8.93676390673e-10, No Iterations 5
ExecutionTime = 809.69 s ClockTime = 1950 s

Interface Courant Number mean: 7.49421107175e-05 max: 0.495849330153
Courant Number mean: 0.00643486555823 max: 0.795353004364
deltaT = 6.99465836359e-06
Time = 0.006397750943

Virtual-iCFD May 1, 2011 11:21

Alpha1 image at timestep=0 is posted below after running setFields.

http://www.cfd-online.com/Forums/mem...rd-hexmesh.htm

http://www.cfd-online.com/Forums/mem...d-hexmesh.html

akidess May 3, 2011 04:49

1e-6 is not necessarily *extremely* small, it depends on your setup. What is the maximum flow velocity you're expecting? Compare that to your smallest cell size. Running with 1e-06s, how does the solution look like? Does it make sense?

JNSN June 10, 2015 08:05

Hi,

some comments:
  1. Are you sure you want to simulate in all six degrees of freedom? If not use constraints
  2. Check your body properties, i.e. mass, center of mass and moments of inertia. The solver output indicates, there is something wrong: rotation velocity around y of 800 rag/s, translation velocity in z of 27 m/s is quite high :-).
  3. Think about your meshing strategy. Have a look at the DTCHull tutorial, how to set up a mesh for free surface flow around a ship. Especially domain size and free surface refinement.
  4. interDyMFoam with semi-implicit MULES is able to handle max Courant numbers up to 100 without stability problem (since v2.3)
  5. If you have a proper mesh (see point 3.), first run with interFoam. If your simulation is running with interFoam, switch to interDyMFoam.

Good luck,
Jan

Henning86 June 12, 2015 04:30

momentumPredictor no;

set the momentumPredictor to yes


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