[N1ckb45]

Hi,

I have been attempting to run simpleFoam over a NACA aerofoil and match it to literature and XFoil data for Re=3e6. After meshing and running what seemed like successful simulations, I still can't get it to match the literature (the pressure drag was almost 10 times too big, although the viscous drag was correct).

I then tried to run the tutorial case given on the openFoam website and I am having the same issue. The user guide claims it is a NACA0012, although the aerofoil downloaded seems much more like a NACA23015 (or another 5-series). Whichever aerofoil I run on XFoil, I still cannot get the tutorial case to come close, and I have not made any changes to the files downloaded.

Any ideas?

Thanks

[HPE]

Could you provide the steps required so that the issue cab be replicated?

[Yann]

Hi folks,

Just in case you missed it, the OpenFOAM.com extended code guide provides a detailed documentation on the airFoil2D tutorial, including validation with literature :
https://www.openfoam.com/documentati...irfoil-2d.html

I didn't try to run it myself so I don't have any opinion about it but it seems this documentation is a good starting point to try to reproduce these results.

Yann

[N1ckb45]

Hi,

I followed the tutorial that Yann has linked me to; the only changes I made were to add the 'forcecoeffs' function into the control dict file (attached) and edit the 0/U file so there is no angle of attack. However, when I run this file I have two issues.

Firstly, when I run paraFoam, the aerofoil is visibly different to that shown on Yann's link (it looks like a slightly cambered 5-series like a NACA 23015).

Secondly, the results outputted are very different from those in the validation literature provided in the link above. The drag coefficient is supposed to be around 0.008, whereas my results are 0.019. The lift coefficient also comes out at 0.247, but should be 0.12. Interestingly, though, the viscous drag matches the results that XFoil gives.

I have attached the last result from the terminal (the whole output was too big a file to attach) and the control dict file.
Thanks,
Nick

[HPE]

Might be one of the links for the mesh is wrong in that tutorial page. I will be able to look at it on Friday. Many thanks for your contribution!

[Yann]

Hi Nick,

The link provides required data to reproduce the case, or at least most of it. (no idea if something is missing)

I had a quick peek at the airfoild2D tutorial and the setup seems to be quite different from what's presented in the documentation, whether it is velocity, transport properties or geometry. It doesn't look like NACA0012, and has a chord of 35m instead of 1m in the documentation. (and in your forceCoeffs function)

I can only suggest you to check your setup and adjust it according to the documentation (starting with the geometry) to reproduce the case in the documentation.


Once you've reproduced these results, you might derive it to fit your own case.


Yann

[HPE]

airfoil2D shouldnt involve NACA0012. This suggests the link is wrong there. On the other hand, the mesh was from NASA Turbulence resource website, for which you can do download, and convert to the OF format.