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I am learning OpenFOAM as a hobby and using my Vespa racing as the topic to apply it to. The objective is to produce modifications that improve the top speed (as well as getting some values such as lift). I am basing my simulation on the motorbike tutorial.

The motorbike tutorial uses the kOmegaSST turbulence model but someone had suggested to me in the past that SpalartAllmaras might be a better choice. I have access to a super computer so saving CPU cycles is not much of an issue for me. Below is a picture of my model (which I am cleaning up). Is kOmegaSST a good enough choice or is there another worth focusing on?

(http://www.openfoam.com/features/RAS.php)!

Vespa 3D Scan

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    $\begingroup$ shouldn't the geometry include the rider for net drag? $\endgroup$ – Subodh May 24 '13 at 10:59
  • $\begingroup$ yes - I have the rider but no where near the resolution of the model (generated from an human animation package called Daz3D). The picture is showing detail which I believe would impact what turbulence model is best to use due to the level of detail. (and yes I am filling all the holes) $\endgroup$ – internetscooter May 25 '13 at 13:27
  • $\begingroup$ If you have access to a super computer, why do you want to stick to RAS instead of using e.g. DES? By the way: Why do you think that SpalartAllmaras might be a better choice? In case of stability or precision? $\endgroup$ – EverythingRightPlace Nov 14 '13 at 11:06
  • $\begingroup$ I think you mean LES? Yes - spoke to a Prof at Monash and he pointed me to LES. OpenFOAM has a LES Motor Bike tut so I am going through that and adapting it to the Vespa (I'll update this when I have it working to a large scale) $\endgroup$ – internetscooter Nov 15 '13 at 21:17
  • $\begingroup$ Yes - the indirect answer to this question is to jump to the LES version provided: $OPENFOAM_DIR/tutorials/incompressible/pisoFoam/les/motorBike. This uses RAS in it's workflow (i.e. it runs the simpleFOAM tut first and makes a copy of the result for the pisoFOAM run) and seems to scale well. My understanding is that LES provides more accurate results on top of RAS, so I am guessing that whatever RAS model is used, as long as it is roughly right, the LES results will take precedence anyway? $\endgroup$ – internetscooter Dec 15 '13 at 22:05

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