[Paraview] wallShearStress Calculation in Paraview

[Andy Bauer]

There's no general way to compute gradients normal to the surface so you
need to compute the gradient on the simulation's cells (e.g. volumetric
cells for 3D). You can use the Gradient Of Unstructured Data set to do
that. Then extract the surface as Mathi said, use the Normals filter to
compute the normals, use the Calculator filter to multiply the normals by
the gradient and the viscosity and you'll have the wall shear stress over
the entire boundary surface. You can then select the cells you want to show
the WSS over the exact portion of the desired boundary.

On Wed, Dec 6, 2017 at 9:05 AM, Ezhilmathi Krishnasamy <
ezhkr601 at student.liu.se> wrote:

> Hi Ahmet,
>
> What you can do that is, use the filter name called extract surface.
> once you get that surface either you can export those values in form of
> from elements or from the points.
>
> It might work, or you may get more clear explanation from this forum.
>
> Cheers,
> Mathi
>
>
>
> On 6 December 2017 at 15:00, Ahmet Ahmet <ahmetskyland at gmail.com> wrote:
>
>> Hello everyone,
>>
>> I have results with OpenFOAM including p,T,U outputs. Due to some
>> reasons, I can't use wallShearStress or wallgradU utility in OF. So, I have
>> to calculate it on Paraview. I saw many topics related to that on google,
>> but I could not find a satisfactory answer. My case is 3-D, compressible
>> and laminar but we can think about incompressible and may be 2-D.
>>
>> I think the most important part for WSS is to calculate velocity
>> gradient. My unsolved problem is to calculate that. How can I calculate
>> gradients on the wall? I have no-slip wall, that is u=0 and with *Gradient
>> of Unstructured DataSet/Compute Derivatives *filters, I obtained 0 on
>> the wall. I think the values in the nearest mesh to the wall should be
>> accounted for. To do that, what should I do?
>>
>> *Note:*
>>
>>    1. The walls are not aligned with a coordinate axis. For this part, I
>>    tried to extract the wall surface and generate normal vectors.
>>    2. As an alternative to get directly on wall, I tried to get slice a
>>    little bit over the wall surface and then take surface vector on slice then
>>    gradient of unstructured dataset on surface vector. That gives me a result
>>    but I am not sure it's true.
>>
>>
>> This may be simple for you, sorry for that.
>> Thank you in advance,
>> Ahmet
>>
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