[Paraview] How does Paraview calculate the velocity gradient

[Christopher Neal]

Hi Wilson,

Perhaps this post contains information that may be helpful?
http://public.kitware.com/pipermail/paraview/2009-January/010608.html

Is the boundary layer in your simulation properly resolved? That steep
gradient near the wall could be smeared out if the proper resolution isn't
used.

-Chris

On Thu, Aug 24, 2017 at 12:49 AM, HongchaoWang <hongchao.wang2013 at gmail.com>
wrote:

> Hi,
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> How does Paraview calculate the velocity gradient if I use filter “gradient of unstructured data set”? And what is the difference between using cell data and point data as input?
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> For my case I am simulating an oscillatory flow inside a narrow channel, I would like to obtain the velocity gradient in order to calculate the shear stress across the channel. I applied the filter “gradient of unstructured data set” and use cell data as input. The results are reasonable for most region in the channel except for the velocity gradient in the first near-wall cell. The value is about half the analytical solution. Why is that?
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> Many thanks,
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> Wilson
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-- 
Christopher Neal
Research Engineer
Streamline Numerics, Inc.
https://www.snumerics.com/
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