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Old   July 2, 2013, 22:41
Default Wall Shear Stress
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Hello Guys,
I just have modelled a basic 3D pipe flow with periodic boundaries. I tried to plot wall shear stress contours and also the xy plots. The flow is laminar. I am somehow not convinced with the contour and plot of wall shear stress. I have plotted them at the outlet. Can anyone comment if the plots are correct or not? Thanks.



-Varad
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Old   July 3, 2013, 06:54
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Since the WALL shear stress is only defined at the wall, evaluating it in the fluid zone will only lead to confusion. What exactly makes you doubt that the results are correct?
The velocity profile looks ok if your bulk velocity is ~1 m/s.
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Old   July 3, 2013, 14:16
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Hii,
Thanks for your reply.I was thinking of getting something like this

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Old   July 4, 2013, 04:09
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This is the shear stress \eta \frac{\partial u}{\partial r}.

This should equal the wall shear stress at the wall (r=R). But again, the variable "WALL shear stress" in fluent (and in fluid dynamics in general) is only defined at the wall and is thus not defined in the fluid.
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Old   July 4, 2013, 13:26
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So how do I plot the shear stress in Fluent?
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Old   July 5, 2013, 03:23
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Among the "derivatives", you should find the velocity derivative \frac{\partial u_i}{\partial x_j} that complies with your coordinate system. Multiply by the dynamic viscosity \eta and thats it.
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Old   July 5, 2013, 09:40
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Thanks a lot for ur replies mate..
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