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Zero value for sigmayy

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Old   January 20, 2009, 11:03
Default Hi everyone, I am studying
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Sébastien Bocquet
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Hi everyone,

I am studying 2D flow around a cylinder. Wind is coming along the x (horizontal) axis. Since I am interested in the drag and lift on the cylinder, I am extracting the pressure and viscous stresses on the cylinder, and computing lift and drag with the forceCoeffs functionObject.

I get viscous stress sigmayy around 10E-20 at any point of the cylinder, whereas sigmaxx and sigmaxy have significant values. To check if sigmayy should actually be zero, I decided to change the wind direction so that it is now along the y axis. I have again in this case significant values for sigmaxx and sigmaxy, and still zero values for sigmayy. The non-zero values for sigmaxx seems to confirm that sigmayy should not be zero.

Further integrating pressure forces and viscous stresses sigmaxx and sigmaxy over the cylinder, I can match the force along x given by forceCoeffs in both cases. However, I cannot match the force along y, which involves sigmaxy and sigmayy. The relative error is significant (around 25%).



Solver/Application:
simpleFoam, laminar case


Platform:
UNIX 64 bit

Version:
OpenFOAM 1.5

Thanks for your answer,

Seb
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Old   January 20, 2009, 12:09
Default There is a possibility that th
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There is a possibility that this issue relates to problems with the symmTensor operators in 1.5 which have already been fixed in 1.5.x so it might be worth giving that a try. If you don't have any luck with 1.5.x could you please post the case here so we can look at the issue in more detail?

H
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Old   January 21, 2009, 03:40
Default Thanks for the information, we
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Sébastien Bocquet
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Thanks for the information, we are trying to install git and update to 1.5.x
I will post the results,

Seb
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