[Alexvader]

Hi

I have created a test case where i wish to track the centrifugal separation of a particulate flow from air.

I have created a mesh, and imposed BCs for icoFoam, i have adjusted the time step in order that the run does not diverges due to high Courant number...

I have used the same settings ( controlDict, mesh, BCs, fvSchemes and fvSolution ) with icoLagrangianFoam, after setting the kinematicCloudproperties, but the run diverges at much smaller time steps... what should i do to prevent this from happening...?

BRGDS

Alex

[Alexvader]

These are the first three iterations using icoLagrangianFoam, from a previously converged icoFoam case, using same time step, mesh, schemes and solution algorithms... :

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.5-dev |
| \\ / A nd | Revision: 1861 |
| \\/ M anipulation | Web: http://www.OpenFOAM.org |
\*---------------------------------------------------------------------------*/
Exec : icoLagrangianFoam
Date : Oct 05 2011
Time : 00:14:02
Host : iskandhar
PID : 21050
Case : /home/alex/OpenFOAM/alex-1.5-dev/run/icoLagrangianFoam/BoxParticles4
nProcs : 1

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

Create mesh for time = 0

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Reading environmentalProperties
Constructing kinematicCloud
--> FOAM Warning :
From function Cloud<ParticleType>::initCloud(const bool checkClass)
in file /home/alex/OpenFOAM/OpenFOAM-1.5-dev/src/lagrangian/basic/lnInclude/CloudIO.C at line 51
Cannot read particle positions file
"/home/alex/OpenFOAM/alex-1.5-dev/run/icoLagrangianFoam/BoxParticles4/0/lagrangian/kinematicCloud"
assuming the initial cloud contains 0 particles.
Selecting DispersionModel NoDispersion
Selecting DragModel SphereDrag
Selecting InjectionModel ConeInjection
Selecting pdfType RosinRammler
Selecting WallInteractionModel StandardWallInteraction
Selecting U IntegrationScheme Euler

Starting time loop

Time = 0.0002

Courant Number mean: 4.23209e-05 max: 0.104846 velocity magnitude: 1.11443
Evolving kinematicCloud

--> Cloud: kinematicCloud
Added 20 new parcels

Cloud name: kinematicCloud
Parcels added during this run = 20
Mass introduced during this run = 6.66667e-06
Current number of parcels = 20
Current mass in system = 6.66667e-06

PBiCG: Solving for Ux, Initial residual = 0.000529261, Final residual = 5.48978e-06, No Iterations 1
PBiCG: Solving for Uy, Initial residual = 0.00100107, Final residual = 1.01479e-07, No Iterations 2
PBiCG: Solving for Uz, Initial residual = 0.00222116, Final residual = 2.36782e-07, No Iterations 2
PCG: Solving for p, Initial residual = 0.0195505, Final residual = 9.85446e-07, No Iterations 414
time step continuity errors : sum local = 1.7666e-10, global = 4.41944e-13, cumulative = 4.41944e-13
PCG: Solving for p, Initial residual = 0.0173523, Final residual = 9.39649e-07, No Iterations 401
time step continuity errors : sum local = 1.68072e-10, global = 3.83983e-13, cumulative = 8.25927e-13
ExecutionTime = 30.61 s ClockTime = 31 s

MassFlows: auto8 = 4.32253e-09 auto9 = -2.4648e-09 auto11 = -9.71808e-10
Time = 0.0004

Courant Number mean: 4.4404e-05 max: 0.476931 velocity magnitude: 11.5557
Evolving kinematicCloud

--> Cloud: kinematicCloud
Added 20 new parcels

Cloud name: kinematicCloud
Parcels added during this run = 40
Mass introduced during this run = 1.33333e-05
Current number of parcels = 40
Current mass in system = 1.33333e-05

PBiCG: Solving for Ux, Initial residual = 0.028415, Final residual = 6.92591e-06, No Iterations 2
PBiCG: Solving for Uy, Initial residual = 0.0303066, Final residual = 4.55824e-06, No Iterations 2
PBiCG: Solving for Uz, Initial residual = 0.0142992, Final residual = 5.03008e-06, No Iterations 2
PCG: Solving for p, Initial residual = 0.0717523, Final residual = 9.43277e-07, No Iterations 437
time step continuity errors : sum local = 1.76544e-10, global = 1.3853e-12, cumulative = 2.21123e-12
PCG: Solving for p, Initial residual = 0.0541759, Final residual = 9.53082e-07, No Iterations 416
time step continuity errors : sum local = 2.06811e-10, global = 7.72575e-13, cumulative = 2.9838e-12
ExecutionTime = 58.33 s ClockTime = 59 s

MassFlows: auto8 = 5.09844e-09 auto9 = -2.40789e-09 auto11 = -9.08051e-10
Time = 0.0006

Courant Number mean: 4.77038e-05 max: 0.932049 velocity magnitude: 27.89
Evolving kinematicCloud

--> Cloud: kinematicCloud
Added 20 new parcels

Cloud name: kinematicCloud
Parcels added during this run = 60
Mass introduced during this run = 2e-05
Current number of parcels = 60
Current mass in system = 2e-05

PBiCG: Solving for Ux, Initial residual = 0.109319, Final residual = 9.01888e-07, No Iterations 3
PBiCG: Solving for Uy, Initial residual = 0.111, Final residual = 8.75318e-07, No Iterations 3
PBiCG: Solving for Uz, Initial residual = 0.0742368, Final residual = 8.70986e-07, No Iterations 3
PCG: Solving for p, Initial residual = 0.391891, Final residual = 9.77096e-07, No Iterations 448
time step continuity errors : sum local = 3.12159e-10, global = -1.4262e-12, cumulative = 1.55761e-12
PCG: Solving for p, Initial residual = 0.228785, Final residual = 9.49803e-07, No Iterations 436
time step continuity errors : sum local = 3.2702e-10, global = 1.93379e-12, cumulative = 3.4914e-12
ExecutionTime = 87.46 s ClockTime = 88 s

MassFlows: auto8 = 7.97621e-09 auto9 = -2.55651e-09 auto11 = -9.58026e-10
Time = 0.0008

Courant Number mean: 8.0158e-05 max: 6.90053 velocity magnitude: 139.132
Evolving kinematicCloud

--> Cloud: kinematicCloud
Added 20 new parcels

Cloud name: kinematicCloud
Parcels added during this run = 80
Mass introduced during this run = 2.66667e-05
Current number of parcels = 47
Current mass in system = 1.56667e-05

PBiCG: Solving for Ux, Initial residual = 0.491305, Final residual = 3.60123e-06, No Iterations 7
PBiCG: Solving for Uy, Initial residual = 0.435496, Final residual = 2.98495e-06, No Iterations 7
PBiCG: Solving for Uz, Initial residual = 0.398934, Final residual = 5.11571e-06, No Iterations 7

It can clearly be seen that Co is getting higher and higher... and what's worse is that i have adjustable time step in my controlDict :

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.2 |
| \\ / A nd | Web: http://www.openfoam.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/

// FoamX Case Dictionary.

FoamFile
{
version 2.0;
format ascii;

root "/home/coyote/hjasak/OpenFOAM/hjasak-1.2/run/test";
case "cavity";
instance "system";
local "";

class dictionary;
object controlDict;
}

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

application icoLagrangianFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 1.5;

deltaT 0.0002;

writeControl timeStep;

writeInterval 20;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

graphFormat raw;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 0.5;

maxDeltaT 0.0002;

functions
(
massFlow
{
type patchMassFlow;
functionObjectLibs
(
"libsimpleFunctionObjects.so"
);
verbose true;
patches
(
auto8
auto9
auto11
);
factor 1;
}
);

What can i do here...?