code_saturne User's Forum

Hello everybody

I'm a quite new using CS and I'm trying to calculate the Drag coefficient of a cylinder. I've found a manner in the CS documentation using Fortran subroutines. Can I calculate it directly from CS GUI?

Kind regards,

Thiago Vasconcellos Birro

Hello,

To directly compute the drag coefficient, you'll need user subroutines.

With the GUI, you can activate computation and postprocessing output of boundary stresses, possibly output on a mesh subset, which you could then use to compute the drag coefficient using a postprocessing tool.

Regards,

Yvan

Hello Yvan

Thanks for replying. I'm looking for information about using the Paraview to calculate the drag coefficient. However, Is there some way to only separate the cylinder surface to integrate on it?

Kind regards,

Birro

Hello,

Yes, you can create a specific postprocessing surface mesh. Under "Calculation Control/Ouput Control" in the GUI using the same selection criteria (i.e. group name) you would use to define the wall boundary condition on the cylinder (assuming you have a specific group for that area).
Using the "separate blocks" filter under ParaView, you can then load just this part, so the integration filters should then be enough to compute the forces you need.

Regards,

Yvan

Hello Yvan
So, I'm testing the advices that you gave me. However, a strange thing happened. I've created the group CYLIN, meaning the internal surface of the Cylinder. So, when I configured CYLIN as an internal surface, the CS produced an error: "SIGSEGV signal (forbidden memory area access) intercepted!" The same group was identified correctly by the preprocessor.log.

Kind Regards

I'm also sending the files

best regards

Hello,

Could you also post your xml file (and mesh if it is not too large) ?

Best regards,

Yvan

Hello everybody

I've had a trouble to send the mesh and the xml here, so I'm sending by a link. For the simulations, I'm using the CS 4.0.6.

https://www.dropbox.com/sh/bc8igqdkgw7o ... bpoca?dl=0


Kind regards

Thiago Birro

Hello,

I fixed the crash, which was related to insufficient checks on the input.

You also need to fix your setup, which will avoid the issue even with the version you have:
the postprocessing output mesh for the cylinder can be named whatever you want, but you need to define it as a mesh of boundary cells, and use CYLIN as a selection criteria.

Regards,

Yvan