# The problem for velocity calculation using turbulent model in openfoam.

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September 4, 2013, 11:18
The problem for velocity calculation using turbulent model in openfoam.
#1
New Member

Maosong Cheng
Join Date: Aug 2012
Posts: 19
Rep Power: 6
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!
Attached Images
 1.jpg (16.2 KB, 12 views) 2.jpg (7.6 KB, 12 views)

Last edited by mscheng; September 10, 2013 at 03:02.

 September 9, 2013, 08:10 #2 New Member   Maosong Cheng Join Date: Aug 2012 Posts: 19 Rep Power: 6 sorry！ the inlet velocity is 0.5m/s. Last edited by mscheng; September 10, 2013 at 03:04.

 September 10, 2013, 02:45 #3 Senior Member   Håkon Strandenes Join Date: Dec 2011 Location: Norway Posts: 111 Rep Power: 11 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. Bernhard likes this.

 September 10, 2013, 03:22 #4 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 what are your BC's? __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

September 10, 2013, 03:49
#5
New Member

Maosong Cheng
Join Date: Aug 2012
Posts: 19
Rep Power: 6
Quote:
 Originally Posted by immortality 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
{
}
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
{
}
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
{
}
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
{
}
outlet
{
type fixedValue;
value uniform 0;
}
inlet
{
}
}
================================================== ========
nu = 1.0631e-6

Thanks!

 September 10, 2013, 08:24 #6 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 blue region is wall? how is grid? __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

September 10, 2013, 08:35
#7
New Member

Maosong Cheng
Join Date: Aug 2012
Posts: 19
Rep Power: 6
Quote:
 Originally Posted by immortality blue region is wall? how is grid?
Hi immortality,
Yes, it is wall.
For the mesh, pls. refer to attached file!

Thanks!
Attached Images
 1.jpg (68.8 KB, 8 views)

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