[sunnysun]

Hi, everyone,

I would like to simulate newtonian,unsteady flow in an asymmetric pipe, could you please give me some ideas which solver I should use? (Now I am thinking of using simpleFoam or turbFoam)

Thanks!!

sunny

[grtabor]

Turbulent or laminar? simpleFoam is a steady-state code, so that would not be appropriate. If your flow is laminar, use icoFoam or turbFoam with the laminar turbulence model switched on. If it is turbulent, use turbFoam.

Gavin

[sunnysun]

Hi, thanks Gavin, my mesh geometry is a straight pipe with a sudden expansion in the middle,which measn the flow is lamina before it goes into expansion, in this case, which solver would be more suitable?

Many thanks!

Sunny

[cedric_duprat]

Hi sunny,

In fact, I think the question is not about your geometry, a very complex one can be laminar and a simple channel can be turbulent. The main point is the Reynolds number which caracterise your flow motion.

Then, the question is what you want to do with your calculation. A mensioned by Gavin, a steady calculation can be enought but some time a unsteady one is better. so what is the physics you need to take into account ?

When you will have an answer of all these questions, it'll be easier to find the solver you will need to use or the solver you will need do make.

hope it helps

Cedric

[sunnysun]

Hi, Cedric,
Thanks fou your reply.
The Reynolds number shows the flow is laminar. What I would like to see is the velocity field and wall shear stress in the expanded section. By the way, may I know how to switch on laminar turbulence model as mentioned by Gavin?

Sorry for this simple question...

Thanks!!

Sunny

[grtabor]

There should be a turbulenceProperties dictionary in the constant directory; change the switch RASModel to "laminar". Alternatively, I think switching turbulence to "off" works as well.

Gavin

[sunnysun]

Hi, Gavin,

Sorry but I could not find the 'RASModel', so I copied the content of turbulenceProperties dictionary in constant directory of turbFoam. If I switch the turbulence to'off', should it generate the same result as icoFoam? Many thanks!

Sunny


FoamFile
{
version 2.0;
format ascii;

root "";
case "";
instance "";
local "";

class dictionary;
object turbulenceProperties;
}

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

turbulenceModel kEpsilon;

turbulence on;

laminarCoeffs
{
}

kEpsilonCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
}

RNGkEpsilonCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.0845;
C1 C1 [0 0 0 0 0 0 0] 1.42;
C2 C2 [0 0 0 0 0 0 0] 1.68;
alphak alphaK [0 0 0 0 0 0 0] 1.39;
alphaEps alphaEps [0 0 0 0 0 0 0] 1.39;
eta0 eta0 [0 0 0 0 0 0 0] 4.38;
beta beta [0 0 0 0 0 0 0] 0.012;
}

kOmegaSSTCoeffs
{
alphaK1 alphaK1 [0 0 0 0 0 0 0] 0.85034;
alphaK2 alphaK1 [0 0 0 0 0 0 0] 1.0;
alphaOmega1 alphaOmega1 [0 0 0 0 0 0 0] 0.5;
alphaOmega2 alphaOmega2 [0 0 0 0 0 0 0] 0.85616;
gamma1 gamma1 [0 0 0 0 0 0 0] 0.5532;
gamma2 gamma2 [0 0 0 0 0 0 0] 0.4403;
beta1 beta1 [0 0 0 0 0 0 0] 0.0750;
beta2 beta2 [0 0 0 0 0 0 0] 0.0828;
betaStar betaStar [0 0 0 0 0 0 0] 0.09;
a1 a1 [0 0 0 0 0 0 0] 0.31;
c1 c1 [0 0 0 0 0 0 0] 10;

Cmu Cmu [0 0 0 0 0 0 0] 0.09;
}

NonlinearKEShihCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphak alphak [0 0 0 0 0 0 0] 1;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76932;
A1 A1 [0 0 0 0 0 0 0] 1.25;
A2 A2 [0 0 0 0 0 0 0] 1000;
Ctau1 Ctau1 [0 0 0 0 0 0 0] -4;
Ctau2 Ctau2 [0 0 0 0 0 0 0] 13;
Ctau3 Ctau3 [0 0 0 0 0 0 0] -2;
alphaKsi alphaKsi [0 0 0 0 0 0 0] 0.9;
}

LienCubicKECoeffs
{
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphak alphak [0 0 0 0 0 0 0] 1;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
A1 A1 [0 0 0 0 0 0 0] 1.25;
A2 A2 [0 0 0 0 0 0 0] 1000;
Ctau1 Ctau1 [0 0 0 0 0 0 0] -4;
Ctau2 Ctau2 [0 0 0 0 0 0 0] 13;
Ctau3 Ctau3 [0 0 0 0 0 0 0] -2;
alphaKsi alphaKsi [0 0 0 0 0 0 0] 0.9;
}

QZetaCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphaZeta alphaZeta [0 0 0 0 0 0 0] 0.76923;
anisotropic no;
}

LaunderSharmaKECoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
}

LamBremhorstKECoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
}

LienCubicKELowReCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphak alphak [0 0 0 0 0 0 0] 1;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
A1 A1 [0 0 0 0 0 0 0] 1.25;
A2 A2 [0 0 0 0 0 0 0] 1000;
Ctau1 Ctau1 [0 0 0 0 0 0 0] -4;
Ctau2 Ctau2 [0 0 0 0 0 0 0] 13;
Ctau3 Ctau3 [0 0 0 0 0 0 0] -2;
alphaKsi alphaKsi [0 0 0 0 0 0 0] 0.9;
Am Am [0 0 0 0 0 0 0] 0.016;
Aepsilon Aepsilon [0 0 0 0 0 0 0] 0.263;
Amu Amu [0 0 0 0 0 0 0] 0.00222;
}

LienLeschzinerLowReCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
alphak alphak [0 0 0 0 0 0 0] 1;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
Am Am [0 0 0 0 0 0 0] 0.016;
Aepsilon Aepsilon [0 0 0 0 0 0 0] 0.263;
Amu Amu [0 0 0 0 0 0 0] 0.00222;
}

LRRCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
Clrr1 Clrr1 [0 0 0 0 0 0 0] 1.8;
Clrr2 Clrr2 [0 0 0 0 0 0 0] 0.6;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
Cs Cs [0 0 0 0 0 0 0] 0.25;
Ceps Ceps [0 0 0 0 0 0 0] 0.15;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
}

LaunderGibsonRSTMCoeffs
{
Cmu Cmu [0 0 0 0 0 0 0] 0.09;
Clg1 Clg1 [0 0 0 0 0 0 0] 1.8;
Clg2 Clg2 [0 0 0 0 0 0 0] 0.6;
C1 C1 [0 0 0 0 0 0 0] 1.44;
C2 C2 [0 0 0 0 0 0 0] 1.92;
C1Ref C1Ref [0 0 0 0 0 0 0] 0.5;
C2Ref C2Ref [0 0 0 0 0 0 0] 0.3;
Cs Cs [0 0 0 0 0 0 0] 0.25;
Ceps Ceps [0 0 0 0 0 0 0] 0.15;
alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923;
alphaR alphaR [0 0 0 0 0 0 0] 1.22;
}

SpalartAllmarasCoeffs
{
alphaNut alphaNut [0 0 0 0 0 0 0] 1.5;
Cb1 Cb1 [0 0 0 0 0 0 0] 0.1355;
Cb2 Cb2 [0 0 0 0 0 0 0] 0.622;
Cw2 Cw2 [0 0 0 0 0 0 0] 0.3;
Cw3 Cw3 [0 0 0 0 0 0 0] 2;
Cv1 Cv1 [0 0 0 0 0 0 0] 7.1;
Cv2 Cv2 [0 0 0 0 0 0 0] 5.0;
}

wallFunctionCoeffs
{
kappa kappa [0 0 0 0 0 0 0] 0.4187;
E E [0 0 0 0 0 0 0] 9;
}


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

[grtabor]

Hi Sunny,

Change the entry

turbulenceModel kEpsilon;

to

turbulenceModel laminar;

Or switch "turbulence" to "off". I think turbulenceModel became RASModel in OF1.5 (I'm still using 1.4.1 myself, so its getting a bit confusing having to check what is what!)

Gavin

[sunnysun]

Hi, Gavin,
Thanks a lot!

I am also using OF1.4.1.

I am still a bit confused~ If I switch the turbulence to'off',or change turbulenceModel kEpsilon to turbulenceModel lamina, should it generate the same result as icoFoam, or what can be the difference?

Thanks!

Sunny