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Old   January 8, 2015, 08:22
Default wall shear stress tensor
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Mohamad Alagheband
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Hi,
I am trying to find every 9 component of a stress tensor on a wall, I read the forum but I didn't get much,all I have ,is Wall Shear X,Y and Z in CFD-post.
Am i missing something or those component are principal ones?
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Old   January 8, 2015, 11:53
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A review of the vocabulary will help:

Normal = Normal unit vector to surface of interest

sigma = stress tensor at a point (9 components, 6 different ones since it should be symmetric for non-polar fluids)

T = stress vector on a point in the surface of interest
= T_normal + T_tangential (3 components)

How are they related ?

T = sigma . Normal (this is a tensor multiplying a vector)

T_normal = T . Normal

T_tangential = T - ( T . Normal )

T_tangential is the Wall Shear vector.

Hope the above helps,
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Old   January 8, 2015, 15:25
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Mohamad Alagheband
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Quote:
Originally Posted by Opaque View Post
A review of the vocabulary will help:

Normal = Normal unit vector to surface of interest

sigma = stress tensor at a point (9 components, 6 different ones since it should be symmetric for non-polar fluids)

T = stress vector on a point in the surface of interest
= T_normal + T_tangential (3 components)

How are they related ?

T = sigma . Normal (this is a tensor multiplying a vector)

T_normal = T . Normal

T_tangential = T - ( T . Normal )

T_tangential is the Wall Shear vector.

Hope the above helps,
I really appreciate your reply,and that was helpful,then what does Wall Shear X,Y and Z exactly mean? sorry if it's stupid question
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Old   January 8, 2015, 16:58
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T = stress vector = force vector per unit area

T_tangential = tangential force vector per unit area
= Wall Shear Vector
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Old   January 9, 2015, 03:34
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Mohamad Alagheband
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Quote:
Originally Posted by Opaque View Post
T = stress vector = force vector per unit area

T_tangential = tangential force vector per unit area
= Wall Shear Vector
Thanks again
I think I ask my question badly,
my real question is how can I find T_xy or other component, in CFD-post i just got Wall Shear X,Y and Z
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