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-   -   The problem for velocity calculation using turbulent model in openfoam. (http://www.cfd-online.com/Forums/openfoam-solving/123107-problem-velocity-calculation-using-turbulent-model-openfoam.html)

mscheng September 4, 2013 11:18

The problem for velocity calculation using turbulent model in openfoam.
 
2 Attachment(s)
Hi FOAMer,

I use standard k-epsilon model to simulate the velocity of a circular tube(R=1.7m,H=4.0m), but I find the velocity near wall in the inlet become bigger than the velocity fixed in the inlet. what is wrong?

thanks!

mscheng September 9, 2013 08:10

sorry! the inlet velocity is 0.5m/s.

haakon September 10, 2013 02:45

I really struggle to get a grip on what the problem really is. Perhaps you could try to reformulate your question/problem? It might as well be good to have some more details.

Perhaps you also could take a closer look on the forum rules? Especially #5 and #8: http://www.cfd-online.com/Forums/misc.php?do=showrules

One last tip: a general idea on how much time you should spend on formulating a question is that you should use as much time formulating your question as you expect people to use on writing answers.

immortality September 10, 2013 03:22

what are your BC's?

mscheng September 10, 2013 03:49

Quote:

Originally Posted by immortality (Post 450838)
what are your BC's?

U BC:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 1 -1 0 0 0 0];
internalField uniform (0 0.5 0);
boundaryField
{
side
{
type fixedValue;
value uniform (0 0 0);
}
outlet
{
type zeroGradient;
}
inlet
{
type fixedValue;
value uniform (0 0.5 0);
}
}

k BC:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -2 0 0 0 0];
internalField uniform 3.75E-003;
boundaryField
{
side
{
type kqRWallFunction;
value uniform 3.75E-003;
}
outlet
{
type zeroGradient;
}
inlet
{
type fixedValue;
value uniform 3.75E-003;
}
}
Epsilon BC:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -3 0 0 0 0];
internalField uniform 1.585453E-004;
boundaryField
{
side
{
type epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 1.585453E-004;
}
outlet
{
type zeroGradient;
}
inlet
{
type fixedValue;
value uniform 1.585453E-004;
}
}
nut BC:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -1 0 0 0 0];
internalField uniform 0;
boundaryField
{
side
{
type nutWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0;
}
outlet
{
type calculated;
value uniform 0;
}
inlet
{
type calculated;
value uniform 0;
}
}
p BC:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -2 0 0 0 0];
internalField uniform 0;
boundaryField
{
side
{
type zeroGradient;
}
outlet
{
type fixedValue;
value uniform 0;
}
inlet
{
type zeroGradient;
}
}
================================================== ========
nu = 1.0631e-6

Thanks!

immortality September 10, 2013 08:24

blue region is wall?
how is grid?

mscheng September 10, 2013 08:35

1 Attachment(s)
Quote:

Originally Posted by immortality (Post 450923)
blue region is wall?
how is grid?

Hi immortality,
Yes, it is wall.
For the mesh, pls. refer to attached file!

Thanks!


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