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sonicFoam aerofoil advice

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Old   May 25, 2010, 05:36
Default sonicFoam aerofoil advice
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Michael Pothitos
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Dear Foamers,

I am trying to evaluate the performance of the sonicFoam solver when applied to a transonic aerofoil case (RAE2822). Using a reasonably fine mesh with the k-epsilon turbulence model I have obtained the attached result (compared with experimental data). The free stream Mach number is 0.75, alpha=2.81, Re=6.5e6.

As you can see, the pressure distribution shows good correlation to the experimental data, however the shock is quite far downstream. Is this a problem with the turbulence model I have used? If so, has anyone any advice on a more suitable model to apply to this problem??


Michael
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Last edited by MikePo; May 26, 2010 at 04:33. Reason: Meant sonicFoam!
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Old   May 25, 2010, 10:43
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Cedric Van Holsbeke
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Wouldn`t SpalartAllmaras be a better turbulence model for your case?

Edit: As cboss said, your mesh can be to fine for the normal k-e model. The Spalart-Allmaras model is modelled to work everywhere (in the regions where your mesh is coarse and in the regions where your mesh is fine)

Last edited by CedricVH; May 25, 2010 at 12:04.
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Old   May 25, 2010, 11:16
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Just to be sure. "Fine mesh" lets me think of a low-Re approach. Are you using OF 1.6, or OF 1.5-dev? I am not that familiar with the k-epsilon model. But I think it is not that easy to set up a low-Re calculation with the k-epsilon model in OF 1.6.(?) (In theory damping has to be included in this case. Not sure how big the error without that will be)

Regards,
Christoph
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Old   May 25, 2010, 11:25
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Michael Pothitos
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I am using 1.6 and have taken onboard your comments about a low-Re case using this release.

Following Cedric's suggestion I am running a case using the SA model. I will let you know my results.
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Old   May 25, 2010, 17:38
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Michael Pothitos
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The results using the SA turbulence model are much smoother, however the shock is still captured too far downstream. In addition, the upper surface suction is over estimated, see below.

Any ideas? Perhaps trying a different solver?
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Old   May 26, 2010, 03:09
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Have you tried rhoCentralFoam?

Check

http://openfoamwiki.net/index.php/TestLucaG

Don't know about simpleFoam, but sonicFoam seems to give the wrong position of the shock.
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Old   May 26, 2010, 03:51
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The link mentions that rhoCentralFoam has been extended to viscous flows, but only laminar... is this still the case or can I use turbulence models in OF 1.6?
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Old   May 26, 2010, 04:26
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Ngoc-Minh Truong
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Just a question: why are you trying a incompressible solver (simpleFoam) when Mach number is .75 ? Are you using simpleFoam or rhoSimpleFoam ?
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Old   May 26, 2010, 04:34
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Michael Pothitos
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Quote:
Originally Posted by truong_nm View Post
Just a question: why are you trying a incompressible solver (simpleFoam) when Mach number is .75 ? Are you using simpleFoam or rhoSimpleFoam ?
Apologies, meant sonicFoam!
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