Wall shear stress value (skin friction)

I want to check the separation and attachment points of the airfoil so i need x-shear stress, y-shear stress, z-shear stress, etc. on the wall as if I get a Pressure field.
Given that vx and vy can be obtained from the [fluidforce], it is expected that the field value can be obtained.
Thank you for letting me know if there’s an easy way how can i get shear stress field

This is a post-processing task. Have PyFR output a single layer of elements around the wall (the region key can accomplish this). Then, export the solution files to VTU and open them up in ParaView. There you can apply the gradient and surface extraction filters to get the quantities of interest.

Regards, Freddie.

Something that can make the surface extraction easier if you are producing you mesh in Pointwise, is you can get Pointwise to export vtu files of all the surfaces. (It’s just a tick box in the gmsh config I think). This makes it much easier to extract the surface you want.

thanks!! i’ll try it

I am using pointwise now. But when i export vtu file and open it in paraview, the parts(surface) are not separated. (Even though i distinguished the parts in pointwise like wall,inlet,outlet…etc)
How can I extract vtu files on each surface? or post processing?

Now I could only get one large domain, not separated parts.

The surface meshes will be exported from Pointwise when you export your mesh to gmsh. They should then be saved in the same place as pointwise saves you gmsh file.

  1. I selected GMSH solver and export CAE ~~.msh file
  2. Pyfr import ~~.msh ~~.pyfrm
  3. after simulation was done, execute command [pyfr ~~.pyfrm ~~.pyfrs ~~.vtu]
  4. I got the vtu file and open it in paraview

In my file, the surface is not devided.

Do you mean to export each surface separately in pointwise? (Maybe that’s not what you mean)
It’s annoying, but can you give me a little more detail?

I pointwise itself in the CAE config options where you normally set the gmsh mesh order, there is also a tick box to export surfaces as vtu. Check that box and when you export the gmsh file from pointwise it will also output vtu files of the surfaces.

thanks i got ~.bin.vtu files.
i try to get shear stress and answer again.

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Hello! Unfortunately, my complex grid was not generated using Pointwise.

I first attempted with a simpler grid, and indeed, I obtained a surface mesh in the generated bin.vtu file. However, because this surface mesh cannot be used in pyFR solver, and the results from pyFR solver are not associated with this surface mesh, I still don’t understand its purpose.

In the VTU output, there are velocity, pressure, and density fields, but what I want to extract is the Skin Friction Coefficient curve. I apologize for my limited physics knowledge, and I’m struggling to understand how to apply the gradient and surface extraction filters to obtain the friction force.

Perhaps I do need assistance, and any help would be greatly appreciated.
Best Regards.