wc34071209 
March 3, 2014 09:25 
Quote:
Originally Posted by alexeym
(Post 477740)
Default value for maxIter is 1000, why limit it? Velocity equation indeed usually converge in 1 iteration, while pressure equation is not so good at it. I wasn't able to find any log file with GAMG for pressure equation but PCG sometimes needs up to 200 iterations (well, GAMG should converge faster).
You can read about it for example here  http://www3.nd.edu/~amoukasi/CBE358_...%20NUMBERS.pdf (actually second Google result for 'Fourier number').
It is used in a stability criterion when solving heat conductivity equation. In OpenFOAM it is called Diffusion Number and you can find definition and usage in chtMultiRegionFoam (solid/solidRegionDiffNo.H).

Thanks!
The reason that I limit it is that I want to save the computational time. If the initial residual is of the order 0.1, then it is easier to fulfill relTol = 0.01 within 20 iterations but hard to get absTol < 1e5.
In the beginning, I did use more inner iterations.
Below I post the residual log.
Code:
/**\
 =========  
 \\ / F ield  OpenFOAM: The Open Source CFD Toolbox 
 \\ / O peration  Version: 2.2.2 
 \\ / A nd  Web: www.OpenFOAM.org 
 \\/ M anipulation  
\**/
Build : 2.2.29240f8b967db
Exec : buoyantPimpleFoam parallel
Date : Feb 28 2014
Time : 23:17:28
Host : "congXXXX"
PID : 2391
Case : /home/cong/OpenFOAM/closedRoom/hotRoom_no2_2nd
nProcs : 4
Slaves :
3
(
"congXXXX.2392"
"congXXXX.2393"
"congXXXX.2394"
)
Pstream initialized with:
floatTransfer : 0
nProcsSimpleSum : 0
commsType : nonBlocking
polling iterations : 0
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring runtime modified files using timeStampMaster
allowSystemOperations : Disallowing usersupplied system call operations
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time
Create mesh for time = 1400.05
Reading g
Reading thermophysical properties
Selecting thermodynamics package
{
type heRhoThermo;
mixture pureMixture;
transport const;
thermo hConst;
equationOfState perfectGas;
specie specie;
energy sensibleEnthalpy;
}
Reading field U
Reading/calculating face flux field phi
Creating turbulence model
Selecting turbulence model type RASModel
Selecting RAS turbulence model kOmegaSST
kOmegaSSTCoeffs
{
alphaK1 0.85034;
alphaK2 1;
alphaOmega1 0.5;
alphaOmega2 0.85616;
Prt 1;
gamma1 0.5532;
gamma2 0.4403;
beta1 0.075;
beta2 0.0828;
betaStar 0.09;
a1 0.31;
b1 1;
c1 10;
F3 false;
}
Calculating field g.h
Reading field p_rgh
Creating field dpdt
Creating field kinetic energy K
No finite volume options present
Selecting radiationModel none
Courant Number mean: 0.00148837580644629 max: 0.0647853339161001
PIMPLE: no residual control data found. Calculations will employ 5 corrector loops
Starting time loop
Courant Number mean: 0.00148837580644629 max: 0.0647853339161001
Time = 1400.051
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 0.000247647843867614, Final residual = 3.999270574318e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 0.000128107979661795, Final residual = 1.83112475255285e07, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.000160633659578868, Final residual = 2.5594269628695e07, No Iterations 1
smoothSolver: Solving for h, Initial residual = 0.000242875086126735, Final residual = 8.06141666995819e07, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0861737029966527, Final residual = 0.000820116649469887, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 7.52141562698942e08, global = 4.91926028910357e09, cumulative = 4.91926028910357e09
GAMG: Solving for p_rgh, Initial residual = 0.0537872793715646, Final residual = 0.000486045277443569, No Iterations 12
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 5.97065178341836e08, global = 4.91556833568525e09, cumulative = 9.83482862478882e09
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 0.000166011564280937, Final residual = 2.11871972688141e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 7.58215157742506e05, Final residual = 9.17281666372826e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 8.86027249173873e05, Final residual = 1.20533099842053e07, No Iterations 1
smoothSolver: Solving for h, Initial residual = 1.60874106858657e05, Final residual = 4.08319969850189e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0572096993313344, Final residual = 0.000502857597070764, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 4.31876336329513e08, global = 2.52631031818182e09, cumulative = 1.23611389429706e08
GAMG: Solving for p_rgh, Initial residual = 0.0368248923460351, Final residual = 0.000339433400191968, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.47307813854051e08, global = 2.5250908689926e09, cumulative = 1.48862298119632e08
PIMPLE: iteration 3
smoothSolver: Solving for Ux, Initial residual = 0.000127060259818226, Final residual = 1.52156840121415e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 5.29445921737536e05, Final residual = 6.47499018761379e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 6.13777747041193e05, Final residual = 7.94535741646234e08, No Iterations 1
smoothSolver: Solving for h, Initial residual = 1.50228683475912e05, Final residual = 3.68357616927878e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0387085517464596, Final residual = 0.000372039926636581, No Iterations 10
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.00267437329372e08, global = 1.60359089444357e09, cumulative = 1.64898207064068e08
GAMG: Solving for p_rgh, Initial residual = 0.0249814364256056, Final residual = 0.000225602225554279, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.27332812053539e08, global = 1.60485248005295e09, cumulative = 1.80946731864598e08
PIMPLE: iteration 4
smoothSolver: Solving for Ux, Initial residual = 9.60615477701421e05, Final residual = 1.17134347180524e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 3.81082635478471e05, Final residual = 4.86568514367135e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 4.49272447238318e05, Final residual = 5.86706411039353e08, No Iterations 1
smoothSolver: Solving for h, Initial residual = 1.46807751471808e05, Final residual = 3.4972415280223e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0266292373137, Final residual = 0.000263811980331065, No Iterations 10
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.17169044295473e08, global = 1.12895991579024e09, cumulative = 1.922363310225e08
GAMG: Solving for p_rgh, Initial residual = 0.0172409016064815, Final residual = 0.000158769948607733, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.62404184000881e08, global = 1.12977978909374e09, cumulative = 2.03534128913438e08
PIMPLE: iteration 5
smoothSolver: Solving for Ux, Initial residual = 0.000121658069251048, Final residual = 2.58614338218384e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 4.71089146736597e05, Final residual = 1.04253715545996e07, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 5.65301129919658e05, Final residual = 1.26714166596492e07, No Iterations 1
smoothSolver: Solving for h, Initial residual = 2.08831375673703e05, Final residual = 7.12911275334731e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0538928262424893, Final residual = 0.000505463810804564, No Iterations 10
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.18557717387552e08, global = 3.50284999781456e10, cumulative = 2.07036978911252e08
GAMG: Solving for p_rgh, Initial residual = 0.00981819390577786, Final residual = 3.97373360009254e05, No Iterations 20
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.43352807596734e09, global = 9.07244129651977e14, cumulative = 2.07037886155382e08
smoothSolver: Solving for omega, Initial residual = 7.77330670381549e06, Final residual = 7.77330670381549e06, No Iterations 0
smoothSolver: Solving for k, Initial residual = 0.000258689105128507, Final residual = 1.04875993446461e06, No Iterations 1
ExecutionTime = 46.12 s ClockTime = 47 s
fieldMinMax volumeMinMax output:
min(p_rgh) = 99822.7698641411 at position (3.06161558808532 3.09883989107467 2.46163835228888) on processor 0
max(p_rgh) = 99824.6394908518 at position (0.0141310859195548 3.11630672402005e19 2.48585301973776) on processor 2
min(p) = 99794.9901934314 at position (2.6125 3.063995781 2.5) on processor 0
max(p) = 99823.7800526305 at position (0.337499959210686 0.0119815945437022 1.59919139963239e18) on processor 2
min(mag(U)) = 0 at position (1.2125 1.4125 4.119968255e18) on processor 0
max(mag(U)) = 0.416412587990551 at position (1.2125 0.00221421732635518 2.4858609322995) on processor 2
min(T) = 288.044594020099 at position (1.93749041958236 0.00246888773684411 0.0377276627556582) on processor 1
max(T) = 307.487743237085 at position (3.06161558808532 3.09883989107467 2.46163835228888) on processor 0
min(CourantNo) = 0 at position (1.21250123476994 1.41249998568824 0.0355901324009811) on processor 0
max(CourantNo) = 0 at position (1.21250123476994 1.41249998568824 0.0355901324009811) on processor 0
min(k) = 7.62163093808797e10 at position (1.7125 2.66249999574979 0.00049999997664166) on processor 0
max(k) = 0.0114244577497563 at position (0.712498589379656 0.0936305427194292 2.40577599472035) on processor 2
min(omega) = 0.203468468793083 at position (1.74994867345548 2.64178641415844 1.15026142133692) on processor 0
max(omega) = 13536.6610183235 at position (3.08539796524394 3.09969118274481 2.48540329051224) on processor 0
Courant Number mean: 0.00148804420017873 max: 0.0647436726007384
Time = 1400.052
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 0.000567342333754088, Final residual = 8.69305596971399e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 0.000245458850194731, Final residual = 3.68077009226284e07, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.000289979601241606, Final residual = 4.48543840988609e07, No Iterations 1
smoothSolver: Solving for h, Initial residual = 0.000296698844680786, Final residual = 6.63764884766414e07, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0740550343777385, Final residual = 0.000725044945148411, No Iterations 13
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.08536056806946e07, global = 3.64075710261366e09, cumulative = 2.43445457181518e08
GAMG: Solving for p_rgh, Initial residual = 0.0440861554067758, Final residual = 0.000393569738811597, No Iterations 14
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 9.04665810010334e08, global = 3.6443093999305e09, cumulative = 2.79888551180823e08
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 0.000169605500762894, Final residual = 2.22207399157954e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 7.50330166453704e05, Final residual = 9.4961785984081e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 9.11322901598886e05, Final residual = 1.22360390214789e07, No Iterations 1
smoothSolver: Solving for h, Initial residual = 2.28734541067651e05, Final residual = 4.83134584065602e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0466962325250491, Final residual = 0.000428205297265179, No Iterations 12
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.94241628736469e08, global = 4.31108721873244e09, cumulative = 3.22999423368148e08
GAMG: Solving for p_rgh, Initial residual = 0.0296053687505284, Final residual = 0.000273806614049499, No Iterations 12
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.06278115018435e08, global = 4.30888049571482e09, cumulative = 3.66088228325296e08
PIMPLE: iteration 3
smoothSolver: Solving for Ux, Initial residual = 9.36392744378687e05, Final residual = 1.06721902570643e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 4.05381191346271e05, Final residual = 4.81158602848071e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 4.71266158880704e05, Final residual = 5.75414949027222e08, No Iterations 1
smoothSolver: Solving for h, Initial residual = 1.8707283656409e05, Final residual = 4.14839197574438e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0303789257000367, Final residual = 0.00028952817806014, No Iterations 10
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.97905019564598e08, global = 3.77192915447232e09, cumulative = 4.03807519870019e08
GAMG: Solving for p_rgh, Initial residual = 0.0196994622428568, Final residual = 0.000180796878584002, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.49826706395044e08, global = 3.77031775813945e09, cumulative = 4.41510697451414e08
PIMPLE: iteration 4
smoothSolver: Solving for Ux, Initial residual = 6.57658865567465e05, Final residual = 7.44857582239132e08, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 2.79973513496785e05, Final residual = 3.38144522082809e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 3.11005630639183e05, Final residual = 3.77439739040657e08, No Iterations 1
smoothSolver: Solving for h, Initial residual = 1.72392202540561e05, Final residual = 3.82872230698463e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.0207323494005721, Final residual = 0.000192916158545086, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.70441030958769e08, global = 3.04867138122196e09, cumulative = 4.71997411263633e08
GAMG: Solving for p_rgh, Initial residual = 0.0136122301209514, Final residual = 0.000131685494725376, No Iterations 11
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.37448318224414e08, global = 3.04971502997717e09, cumulative = 5.02494561563405e08
PIMPLE: iteration 5
smoothSolver: Solving for Ux, Initial residual = 7.68948138911585e05, Final residual = 1.33500514434639e07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 3.40276188770903e05, Final residual = 6.42473722745575e08, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 3.51279835293852e05, Final residual = 6.60143270214444e08, No Iterations 1
smoothSolver: Solving for h, Initial residual = 2.37990891762838e05, Final residual = 7.68148021791493e08, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.055789102927055, Final residual = 0.000504421961352279, No Iterations 10
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.12535425574358e08, global = 2.38263857305886e10, cumulative = 5.00111922990346e08
GAMG: Solving for p_rgh, Initial residual = 0.00952195362129172, Final residual = 3.83661907765528e05, No Iterations 20
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.30631834598393e09, global = 1.59539024230693e13, cumulative = 5.00113518380589e08
smoothSolver: Solving for omega, Initial residual = 3.85169919171067e06, Final residual = 3.85169919171067e06, No Iterations 0
smoothSolver: Solving for k, Initial residual = 0.000215175969522929, Final residual = 8.68436227091422e07, No Iterations 1
ExecutionTime = 85.53 s ClockTime = 86 s
