[Grimoli]

Hello guys.What's up??

So,I'm doing a casa using chtMultiRegionFoam and the problem it's that the casa is taking too much for run (its like 600 seg now to increase 0.01s).

The problem is that it didn't took so much from time 0 to 200,but after this time it's taking too much.

What I'm doing wrong??

Thats my controlDict

application     chtMultiRegionFoam;

startFrom       latestTime;

startTime       0.001;

stopAt          endTime;

endTime         2000;

deltaT          1;

writeControl    adjustableRunTime;

writeInterval   200;

purgeWrite      0;

writeFormat     ascii;

writePrecision  8;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

maxCo           0.3;

// Maximum diffusion number
maxDi           10.0;

adjustTimeStep  yes;

[Linse]

Hello Gabriel,

Is it possible that it is simply due to the physics getting more difficult after 200 seconds?

First of all, I would suggest having a look at the size of your timesteps. Do they remain the same or is there a strong change after these 200 s?
Is there some special process happening around that time?
Does maybe the flow start to interact with a specific boundary for the first time?

As the case starts to run nicely for quite some time, I would guess rather for a physical than a only numerical phenomenon...

[Grimoli]

Man actually it starts on 200 and i dont know why this is happening


look

Create time

Create fluid mesh for region topAir for time = 200

Create solid mesh for region heater for time = 200

*** Reading fluid mesh thermophysical properties for region topAir

    Adding to thermoFluid

Selecting thermodynamics package hRhoThermo<pureMixture<constTransport<specieThermo<hConstThermo<perfectGas>>>>>
    Adding to rhoFluid

    Adding to kappaFluid

    Adding to UFluid

    Adding to phiFluid

    Adding to gFluid

    Adding to turbulence

Selecting turbulence model type laminar
    Adding to ghFluid

    Adding to ghfFluid

Selecting radiationModel none
    Adding to KFluid

    Adding to dpdtFluid

*** Reading solid mesh thermophysical properties for region heater

    Adding to thermos

Constructed constSolidThermo with
    rho        : rho [1 -3 0 0 0 0 0] 2770
    Cp         : Cp [0 2 -2 -1 0 0 0] 875
    K          : K [1 1 -3 -1 0 0 0] 177
    Hf         : Hf [0 2 -2 0 0 0 0] 1
    emissivity : emissivity [0 0 0 0 0 0 0] 1
    kappa      : kappa [0 -1 0 0 0 0 0] 0
    sigmaS     : sigmaS [0 -1 0 0 0 0 0] 0

Region: topAir Courant Number mean: 1286484.7 max: 3599920.8
Region: heater Diffusion Number mean: 4.1794706 max: 7.3027334
Region: topAir Courant Number mean: 1286484.7 max: 3599920.8
Region: heater Diffusion Number mean: 4.1794706 max: 7.3027334
deltaT = 1.6667033e-05
--> FOAM Warning : 
    From function Time::operator++()
    in file db/Time/Time.C at line 1010
    Increased the timePrecision from 6 to 8 to distinguish between timeNames at time 200.00002
Time = 200.00002


Solving for fluid region topAir
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.019716232, Final residual = 1.6403656e-09, No Iterations 3
DILUPBiCG:  Solving for Uy, Initial residual = 0.012907232, Final residual = 2.2705694e-09, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.013200798, Final residual = 2.2197342e-09, No Iterations 3
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 6.4399827e-08, No Iterations 3
Min/max T:293.75167 297.58037
GAMG:  Solving for p_rgh, Initial residual = 0.99787356, Final residual = 0.0047753112, No Iterations 2
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 2.0955263e-05, global = 3.7817856e-07, cumulative = 3.7817856e-07
GAMG:  Solving for p_rgh, Initial residual = 0.016060158, Final residual = 3.3992008e-08, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 2.9962701e-10, global = 2.3043454e-11, cumulative = 3.782016e-07

Solving for solid region heater
DICPCG:  Solving for T, Initial residual = 3.6343786e-06, Final residual = 1.1074279e-10, No Iterations 1
DICPCG:  Solving for T, Initial residual = 1.1077305e-10, Final residual = 1.1077305e-10, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 297.40577 max(T) [0 0 0 1 0 0 0] 297.58611
ExecutionTime = 0.74 s  ClockTime = 1 s

Region: topAir Courant Number mean: 0.10543579 max: 0.29969014
Region: heater Diffusion Number mean: 3.4829688e-07 max: 6.085745e-07
deltaT = 1.6684266e-05
Time = 200.00003


Solving for fluid region topAir
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.022884831, Final residual = 9.3833069e-09, No Iterations 3
DILUPBiCG:  Solving for Uy, Initial residual = 0.010520738, Final residual = 3.5012258e-09, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.015008762, Final residual = 4.8177765e-09, No Iterations 3
DILUPBiCG:  Solving for h, Initial residual = 0.93077846, Final residual = 4.747713e-08, No Iterations 3
Min/max T:288.58434 298.34211
GAMG:  Solving for p_rgh, Initial residual = 0.24296155, Final residual = 0.00114548, No Iterations 2
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 1.2875481e-05, global = 7.0525708e-07, cumulative = 1.0834587e-06
GAMG:  Solving for p_rgh, Initial residual = 0.0062234291, Final residual = 2.3620126e-08, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 3.2396135e-10, global = 1.0592143e-11, cumulative = 1.0834693e-06

Solving for solid region heater
DICPCG:  Solving for T, Initial residual = 3.6308495e-06, Final residual = 1.1095086e-10, No Iterations 1
DICPCG:  Solving for T, Initial residual = 1.1097815e-10, Final residual = 1.1097815e-10, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 297.40574 max(T) [0 0 0 1 0 0 0] 297.58611
ExecutionTime = 1.04 s  ClockTime = 1 s

Region: topAir Courant Number mean: 0.10473279 max: 0.30001713
Region: heater Diffusion Number mean: 3.4865699e-07 max: 6.0920372e-07
deltaT = 1.6683312e-05
Time = 200.00005


Solving for fluid region topAir
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.031291444, Final residual = 3.7406937e-09, No Iterations 3
DILUPBiCG:  Solving for Uy, Initial residual = 0.0091084812, Final residual = 1.274611e-09, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.015709632, Final residual = 8.6319992e-08, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 0.28210003, Final residual = 2.9042804e-08, No Iterations 3
Min/max T:286.3445 299.81416
GAMG:  Solving for p_rgh, Initial residual = 0.1095372, Final residual = 0.00045743401, No Iterations 2
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 6.9504841e-06, global = -6.3899447e-07, cumulative = 4.4447479e-07
GAMG:  Solving for p_rgh, Initial residual = 0.0027215751, Final residual = 6.3309422e-08, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 1.0585492e-09, global = -1.1663625e-11, cumulative = 4.4446313e-07

Solving for solid region heater
DICPCG:  Solving for T, Initial residual = 3.61613e-06, Final residual = 1.1103697e-10, No Iterations 1
DICPCG:  Solving for T, Initial residual = 1.1102969e-10, Final residual = 1.1102969e-10, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 297.40574 max(T) [0 0 0 1 0 0 0] 297.58611
ExecutionTime = 1.34 s  ClockTime = 1 s

I dont know if the physics it's getting harder,look after couples of times running.I think it's wrong,why it's taking so much for the time increase??

Solving for solid region heater
DICPCG:  Solving for T, Initial residual = 0.005962909, Final residual = 6.4298462e-08, No Iterations 3
DICPCG:  Solving for T, Initial residual = 6.4301823e-08, Final residual = 6.4301823e-08, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 297.58905 max(T) [0 0 0 1 0 0 0] 297.75865
ExecutionTime = 10456.83 s  ClockTime = 20373 s

Region: topAir Courant Number mean: 0.10320765 max: 0.29940122
Region: heater Diffusion Number mean: 0.00019795758 max: 0.00034588864
deltaT = 0.009491718
Time = 204.58451


Solving for fluid region topAir
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.0015396868, Final residual = 2.4122723e-08, No Iterations 3
DILUPBiCG:  Solving for Uy, Initial residual = 0.0015750902, Final residual = 3.1655252e-08, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.0023601181, Final residual = 2.7159216e-09, No Iterations 4
DILUPBiCG:  Solving for h, Initial residual = 0.00090606878, Final residual = 6.7778798e-08, No Iterations 3
Min/max T:294.39272 297.75342
GAMG:  Solving for p_rgh, Initial residual = 0.0030871382, Final residual = 1.8547293e-05, No Iterations 4
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 3.668456e-08, global = -1.1708255e-09, cumulative = 5.6651223e-06
GAMG:  Solving for p_rgh, Initial residual = 0.00030016909, Final residual = 1.8205206e-07, No Iterations 1000
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (topAir): sum local = 4.5529577e-10, global = 1.4817097e-12, cumulative = 5.6651238e-06

Solving for solid region heater
DICPCG:  Solving for T, Initial residual = 0.0059749451, Final residual = 6.4717639e-08, No Iterations 3
DICPCG:  Solving for T, Initial residual = 6.4721001e-08, Final residual = 6.4721001e-08, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 297.58946 max(T) [0 0 0 1 0 0 0] 297.75904
ExecutionTime = 10553.9 s  ClockTime = 20590 s

Region: topAir Courant Number mean: 0.10317321 max: 0.29940631
Region: heater Diffusion Number mean: 0.00019835178 max: 0.00034657743
deltaT = 0.0095101952
Time = 204.59402

[Grimoli]

how do i change time steps??

[Linse]

The time-step change in your case is automatic (adjustTimeSteps-setting).
To what I know you either can introduce a fixed timestep (switch of the adjustment) or you can use the automatic control for it.

Concerning your case: The timestep is decreased for some reason (control of the Courant number needs it). What is the reason I can not tell. At that moment the size of the timestep is not yet crazy. So if the simulation doesn't diverge, I would say it's a case of tough luck that the physics needs smaller timesteps for simulating it properly...

[Antimony]

Hi,

The reason it starts from 200 is because in your controlDict your startFrom is set to latestTime. I assume you have a save at time 200 and so if you restarted your simulation using the same parameters (including the ones in the controlDict), it would start from time 200.

Regards,

Antimony