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kalyangoparaju February 7, 2012 00:01

Numerical Schemes for Vortex Capturing
Hi all,

I am trying to model the wing tip vortices from a round tip wing ( NACA 0012) using OpenFOAM. I tried both the Spalart Allmaras and KW-SST models and realized that the results are no where near the experimental results.

When I tweaked the fvSchemes file, I got results which are at least comparable to the experiment but they are still quite a bit away. I understand that the diffusion of the vortex depends majorly on the diverging schemes. I am using Gauss QUICK and when I use MUSCL, the solution blows up.

Can anyone suggest what schemes I can employ to get lower diffusion?


vinz February 7, 2012 02:48

You might also want to look at your mesh in this region since it will play an important role.

kalyangoparaju February 7, 2012 10:19


Thanks for the reply. I have a pretty good mesh and I am confident to an extent that it is not a mesh problem


vinz February 7, 2012 10:38

Out of curiosity, do you have some pictures of the mesh in this region?

kalyangoparaju February 7, 2012 11:45

2 Attachment(s)

Here are some pics of the mesh.

The first mesh is around the wing with a cylinder over the round tip.

The second mesh is in the wake behind the wing, with the fine mesh in the region of the vortex.

Please excuse the weirdness of the cells, since paraview doesn't render well. The mesh was made in snappyHex

Attachment 11156

Attachment 11157

vinz February 7, 2012 12:01

Ok, thanks for images. A small tip for paraview, you can use "extract cell by region" instead of "Slice". It will keep the cells instead of cutting them.

When you say "the results are no where near the experimental results."
What are the parameters that your are looking at? forces? coefficients? flow topology? vortex shedding?

kalyangoparaju February 7, 2012 12:08


Thanks for the tip.

The main parameters which I was comparing were the Normalized axial velocity through the vortex core and the cross flow velocity through the vortex core.

Immediately behind the wing, the norm. axial velocity is around 1.77*U, I get around 1.74*U which is very reasonable but at around x/c=0.6 downstream of the wing, the experimental results have 1.69*U and I have around 0.2-0.3 *U which is a clear indicator of over diffusion either due to the turbulence modeling or the numerical method.

I used both the SA and the KW-SST model with Gauss linear and Gauss QUICK conditions. Gauss QUICK gives slightly better results compared to the Gauss linear but not drastically different.

One thing to note, the residuals have flat lined in just around 600 iterations are about 10e-2 which is not really a good convergence criterion considering the basic geometry involved,and they dont even change. I am running a steady state simulation by the way.

Do you think I need to run a transient ?

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