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Old   August 25, 2011, 05:13
Default Wrong boundary conditions?
  #1
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Hello Foamers,

I want to simulate the flow through a heat exchanger and have already implemented the geometry in OpenFoam.
One part of the heat exchanger looks like the letter U. In this area I got the attached result. The picture shows a slide through the pipe.
I am confused about the flow pattern, because I expected an increase of the velocity at the edge of the curved tube.
Can this be caused by the boundary conditions?
Simulation with: SimpleFoam + k-epsilon for turbulence

Boundary conditions:


U:
boundaryField
{

inlet
{
type fixedValue;
value uniform (1.088250128 0 0);
}

outlet
{
type zeroGradient;
}


Walls
{
type fixedValue;
value uniform (0 0 0);
}

symmetric
{
type symmetryPlane;
}

frontAndBack
{
type empty;
}
}


p:
dimensions [0 2 -2 0 0 0 0];

internalField uniform 101.3;

boundaryField
{
inlet
{
type zeroGradient;
}

outlet
{
type fixedValue;
value uniform 101.3;
}

Walls
{
type zeroGradient;
}

symmetric
{
type symmetryPlane;
}

frontAndBack
{
type empty;
}
}

The frontAndBack-Patch is not in use anymore.

Thanks for your help and good ideas,

Thomas
Attached Images
File Type: jpg Simulation.jpg (54.4 KB, 46 views)
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Old   August 28, 2011, 07:17
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  #2
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Alex
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Hello Thomas,

I am a beginner in OpenFOAM but for me the boundary conditions look okay and I also agree to you that the results look strange. I would would expect an increase of the velocity. The only thing is, I would change the pressure outlet boundary condition to "$internalField" than "uniform 101.23".

What is your convergence criteria and the "symmetric" part of your geometry?

Regards,

Alex
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