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-   -   setting BC for T field (http://www.cfd-online.com/Forums/openfoam/111317-setting-bc-t-field.html)

aujamal20 January 3, 2013 11:04

setting BC for T field
 
4 Attachment(s)
Dear

I am working on a 2D wedge germetry having an inlet at the top and an outlet at the bottom of the wedge.

U and T file are given below.....

Quote:

internalField uniform 573.15;

boundaryField
{
front
{
type wedge;
}
back
{
type wedge;
}
wall
{
type zeroGradient;
}
axis
{
type empty;
}
inlet
{
type fixedValue;
value uniform 823.15;
}
outlet
{
type zeroGradient;
}
top
{
type zeroGradient;
}
bottom
{
type zeroGradient;
}
baffle_lower
{
type zeroGradient;
}
baffle_upper
{
type zeroGradient;
}
}

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


internalField uniform (0 0 0);

boundaryField
{
front
{
type wedge;
}
back
{
type wedge;
}
wall
{
type fixedValue;
value uniform (0 0 0);
}
axis
{
type empty;
}
inlet
{
type fixedValue;
value uniform (0 -1 0);
}
outlet
{
type zeroGradient;
}
top
{
type fixedValue;
value uniform (0 0 0);
}
bottom
{
type fixedValue;
value uniform (0 0 0);
}
baffle_lower
{
type fixedValue;
value uniform (0 0 0);
}
baffle_upper
{
type fixedValue;
value uniform (0 0 0);
}
}
The problem is as the simulation runs and the temperature of fluid increases to max value of 823 K or round about it. The value of temperatue at outlet patch increases further beyond the acceptable range (948K). Which I feel is not right.
I am using a solver which is a combination of buoyantPimpleFoam and buoyantBousi..PimpleFoam and I hope its working well.
I think I need to review boundary conditions of T and U, but ??
Please let me know how I can fix this problem...

Tushar@cfd January 4, 2013 06:29

Can you please, elaborate your problem?

As, it appears to me that a heated fluid enters the wedge, but I am bit confuse with the flow direction.

inlet
{
type fixedValue;
value uniform (0 -1 0);
}
where excatly the fluid is flowing??

Bernhard January 4, 2013 08:58

Can you maybe show a piece of your log file? Is the solution converged?

aujamal20 January 4, 2013 12:18

Dear

Fluid is entering the wedge vertically downward through an inlet patch which is located at left top corner and leaving the wedge vertically from an outlet patch located at left bottom corner.
Initial condition for inlet patch for U is (0 -1.0 0) and T is 823.15K and internal field value is 573.15K. As the simulation runs internal temperature increases which is obvious. And as simulation runs further the temperature at outlet patch increases (more than 900K) beyond the initially defined inlet temperature which is 823.15K.
Which I think is not correct.

Thanks

Tushar@cfd January 4, 2013 23:24

Hello aujamal,
 
Thanks for explaining it again.

I think you need to see for setfieldsdict.


Best regards,
Tushar

aujamal20 January 8, 2013 03:55

http://www.cfd-online.com/Forums/C:%...arametricWedgeDear

Here is a piece of log file ...
Quote:

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 2.1.0-bd7367f93311
Exec : buoyantRhoPimpleFoam
Date : Jan 08 2013
Time : 09:43:27
Host : "sx600.ise.fhg.de"
PID : 11754
Case : /opt/OpenFOAM/adin-2.1.0/run/parametricWedge_0
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

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

Create mesh for time = 2200


Reading g
Reading thermophysical properties

Selecting thermodynamics package hRhoThermo<pureMixture<icoPoly8ThermoPhysics>>
Reading field T

Reading field U

Reading/calculating face flux field phi

Creating turbulence model

Selecting turbulence model type RASModel
Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
Cmu 0.09;
C1 1.44;
C2 1.92;
C3 -0.33;
sigmak 1;
sigmaEps 1.3;
Prt 7;
}

Calculating field g.h

Reading field p_rgh

End of createFields.H

Jamal

Creating field kinetic energy K

Courant Number mean: 0.00111825 max: 0.479457

PIMPLE: Operating solver in PISO mode


Starting time loop

Courant Number mean: 0.00111825 max: 0.479457
deltaT = 0.00591366
Time = 2200.01

DILUPBiCG: Solving for Ux, Initial residual = 7.38743e-05, Final residual = 1.33071e-09, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 4.11304e-05, Final residual = 1.11325e-10, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000473126, Final residual = 4.76594e-09, No Iterations 2
DILUPBiCG: Solving for h, Initial residual = 3.46889e-05, Final residual = 2.47058e-11, No Iterations 2
DICPCG: Solving for p_rgh, Initial residual = 0.141314, Final residual = 0.00136666, No Iterations 106
time step continuity errors : sum local = 0.00140793, global = -0.00138869, cumulative = -0.00138869
DILUPBiCG: Solving for h, Initial residual = 8.33566e-06, Final residual = 5.40919e-09, No Iterations 1
DICPCG: Solving for p_rgh, Initial residual = 0.0992135, Final residual = 9.33209e-09, No Iterations 148
time step continuity errors : sum local = 0.00138889, global = -0.00138889, cumulative = -0.00277758
DILUPBiCG: Solving for epsilon, Initial residual = 9.09699e-06, Final residual = 1.88175e-09, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 6.66571e-06, Final residual = 1.25591e-11, No Iterations 2
ExecutionTime = 0.34 s ClockTime = 1 s

Courant Number mean: 0.00116574 max: 0.501218
deltaT = 0.00589622
--> FOAM Warning :
From function Time::operator++()
in file db/Time/Time.C at line 982
Increased the timePrecision from 6 to 7 to distinguish between timeNames at time 2200.01
Time = 2200.012

DILUPBiCG: Solving for Ux, Initial residual = 2.12558e-05, Final residual = 3.79445e-10, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1.27341e-05, Final residual = 1.75434e-11, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000470895, Final residual = 4.76158e-09, No Iterations 2
DILUPBiCG: Solving for h, Initial residual = 3.47865e-05, Final residual = 1.5689e-11, No Iterations 2
DICPCG: Solving for p_rgh, Initial residual = 0.0990315, Final residual = 0.000840042, No Iterations 107
time step continuity errors : sum local = 0.00139858, global = -0.00138675, cumulative = -0.00416432
DILUPBiCG: Solving for h, Initial residual = 6.74023e-06, Final residual = 4.74838e-09, No Iterations 1
DICPCG: Solving for p_rgh, Initial residual = 0.0991621, Final residual = 8.4887e-09, No Iterations 148
time step continuity errors : sum local = 0.00138691, global = -0.00138691, cumulative = -0.00555124
DILUPBiCG: Solving for epsilon, Initial residual = 9.52191e-06, Final residual = 5.3796e-09, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 6.80848e-06, Final residual = 1.40935e-11, No Iterations 2
ExecutionTime = 0.47 s ClockTime = 1 s
.
.
.
.
Quote:

Courant Number mean: 0.00143896 max: 0.483954
deltaT = 0.00733062
Time = 2209.993

DILUPBiCG: Solving for Ux, Initial residual = 1.90169e-05, Final residual = 6.93929e-10, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1.06757e-05, Final residual = 1.45057e-10, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000900226, Final residual = 7.76524e-09, No Iterations 2
DILUPBiCG: Solving for h, Initial residual = 3.84998e-05, Final residual = 3.13387e-10, No Iterations 2
DICPCG: Solving for p_rgh, Initial residual = 0.087053, Final residual = 0.000738979, No Iterations 107
time step continuity errors : sum local = 0.00175677, global = -0.00174195, cumulative = -4.77239
DILUPBiCG: Solving for h, Initial residual = 8.49488e-06, Final residual = 9.69063e-09, No Iterations 1
DICPCG: Solving for p_rgh, Initial residual = 0.0875056, Final residual = 7.44523e-09, No Iterations 148
time step continuity errors : sum local = 0.00174216, global = -0.00174215, cumulative = -4.77414
DILUPBiCG: Solving for epsilon, Initial residual = 1.04161e-05, Final residual = 1.3093e-11, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 7.40003e-06, Final residual = 8.85286e-09, No Iterations 1
ExecutionTime = 199.36 s ClockTime = 200 s

Courant Number mean: 0.00143899 max: 0.485206
deltaT = 0.00733062
Time = 2210

DILUPBiCG: Solving for Ux, Initial residual = 1.89518e-05, Final residual = 6.90242e-10, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1.09374e-05, Final residual = 1.27851e-10, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000898223, Final residual = 7.8873e-09, No Iterations 2
DILUPBiCG: Solving for h, Initial residual = 3.92578e-05, Final residual = 1.89296e-10, No Iterations 2
DICPCG: Solving for p_rgh, Initial residual = 0.0872695, Final residual = 0.000782768, No Iterations 107
time step continuity errors : sum local = 0.0017604, global = -0.00174469, cumulative = -4.77588
DILUPBiCG: Solving for h, Initial residual = 8.69357e-06, Final residual = 9.99082e-09, No Iterations 1
DICPCG: Solving for p_rgh, Initial residual = 0.0876178, Final residual = 7.68059e-09, No Iterations 148
time step continuity errors : sum local = 0.0017449, global = -0.0017449, cumulative = -4.77762
DILUPBiCG: Solving for epsilon, Initial residual = 9.95682e-06, Final residual = 7.57553e-09, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 6.62671e-06, Final residual = 8.48709e-09, No Iterations 1
ExecutionTime = 199.57 s ClockTime = 200 s

End

aujamal20 January 8, 2013 04:04

http://www.cfd-online.com/Forums/C:%...ametricWedge/0http://www.cfd-online.com/Forums/dat...AAAElFTkSuQmCC

fabian_roesler January 8, 2013 10:22

combined solvers?
 
Hi,

so you combined buoyantBoussinesPimpleFoam with buoyantPimpleFoam for what purpose? Could this cause your problems? Some wrong defined conservation equation?

Regards

Fabian

aujamal20 January 24, 2013 14:39

alphaEff
 
3 Attachment(s)
Dear

You are right, I have combined the buoyantBoussinesqPimpleFoam with buoyantPimpleFoam in order to simulate an incompressible flow with temperature dependent density field. I have included pEqn, UEqn and hEqn in this solver.

Right now every thing seems to be allright as I can run the simulation using the kEpsilon model and T and rho fields looks good to me. But the value of turbulent thermal diffusion (alphat) is too big.

Would you tell me that how the alphaEff is calculated in the following equation of hEqn file

(
fvm::ddt(rho, h)
+ fvm::div(phi, h)
- fvm::laplacian(turbulence->alphaEff(), h)
==
- (fvc::ddt(rho, K) + fvc::div(phi, K))
);

as alphaEff=alphat+alpha according to doxygen and alphat is calculated by kEpsilon as alphat_ = mut_/Prt. What about alpha and why the value of alphat (turbulent thermal diffusion) is out of range. I am using the Prt value 7.0 in fluid RASproperties.
I have attached a temp profile and rho profile and alphat just to show the simulation results.

Please let me know what I have to consider to solve this problem

Regards
Jamal

aujamal20 February 20, 2013 14:59

Dear OFrs
I am working on heat transfer multiregion case containg one fluid and two different solid regions. The solid regions have different thermodynamic properties as one of them is steel and other one is insulation region. So I need to have thermophysicalProperties file in constant folder but the problem is that I am unable to understand char and pmma key words.
Can somebody explain what these things are and how their values can influence the simulation...
Thanks in anticipation...

Ahmed Khattab February 20, 2013 16:25

Quote:

Originally Posted by aujamal20 (Post 409153)
Dear OFrs
I am working on heat transfer multiregion case containg one fluid and two different solid regions. The solid regions have different thermodynamic properties as one of them is steel and other one is insulation region. So I need to have thermophysicalProperties file in constant folder but the problem is that I am unable to understand char and pmma key words.
Can somebody explain what these things are and how their values can influence the simulation...
Thanks in anticipation...

Hi,
I met dame problem before with the same solver.but no one answered me. afer some search i found that these values may be the contribution of two different species in the solid region.
Please share any other answer if you meet any answer in you way.
Good luck :)


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