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Old   December 13, 2007, 09:36
Default Wall Shear stress argument.
  #1
Dimitrios K. Fytanidis
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Dear all,

i'm working on a project, in which i have to use the value of wall shear stress (wss) in a UDF. The main problem is that i can not find the wss argument name. Could anyone tell me the name of this particular variable? Of course, i have already unsuccesfully check the User guide.

Thank in advance for your variable help.

Dimitrios K. Fytanidis
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Old   December 14, 2007, 09:37
Default Re: Wall Shear stress argument.
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szz
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Hi Dimitrios,

with this command you can retrieve the wall shear stress of a certain face f, e.g. in a loop over all faces of a thread tf.

The result is a 3D-Vector (there should be one for 2D as well), here the components are stored separately:

F_x = F_STORAGE_R_N3V(f,tf,SV_WALL_SHEAR)[0]; F_y = F_STORAGE_R_N3V(f,tf,SV_WALL_SHEAR)[1]; F_z = F_STORAGE_R_N3V(f,tf,SV_WALL_SHEAR)[2];

Hope this helps,

Regards szz
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Old   December 14, 2007, 13:37
Default Re: Wall Shear stress argument.
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Dimitrios K. Fytanidis
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Thank you szz, But could you please tell me if these are stresses or forces. I check them and i found really strange results. Generally, I need the value of the component of Wall Shear Stress. Thank you in advance for your variable help.

Dimitrios
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Old   December 15, 2007, 09:04
Default Re: Wall Shear stress argument.
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szz
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Hi,

sorry, it's the forces of course.

Dividing by the area should be possible for both the overall force and the components.

F_AREA(A, f, tf); area = NV_MAG(A);

I have found that although the value is accurate one has to be careful about the sign of the shear forces.

Regards szz.

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Old   December 16, 2007, 10:33
Default Re: Wall Shear stress argument.
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Dimitrios K. Fytanidis
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Thank you szz!!!

Your help was really as usefull as valiable!!!

Regards,

Dimitrios
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