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Old   February 28, 2007, 15:43
Default Best code for Cd calculations?
  #1
HSeldon
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Hi, Im dealing with 2d airfoils with and without flaps and slats. Fluent doesnt give me good results regarding the drag coeff, so I would like to know about your experiences about that, and wich code is the best to get that number.

Thanks!
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Old   March 1, 2007, 20:47
Default Re: Best code for Cd calculations?
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buch
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Hi,

The drag computation relies on many aspects. The computed properties of your boundary layers will have such an impact on your results that I do not think changing software will really be a solution.

Try other meshes (with points enough in the BL, and a correct first grid cell size in the wall-normal direction), and other turbulence models.

Anyway, for complex flows such as airfoils with high-lift devices, I have seen some papers for which the drag value on each element (for example on a 3 elements airfoil) was quite wrong, but with error compensation the overall drag value was quite ok ... Scaring.

Regards
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Old   March 1, 2007, 20:52
Default Re: Best code for Cd calculations?
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HSeldon
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Hi buch, Yes, I tried all what you said (all kind of meshes, different turb models, etc) Right now Im using Fluent, and I heard that others codes use differents approaches to calculate the Cd with better results than Fluent.

Ill keep trying! Thanks
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Old   March 3, 2007, 10:21
Default Re: Best code for Cd calculations?
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Charles
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Have you tried MSES?
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Old   March 3, 2007, 23:34
Default Re: Best code for Cd calculations?
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HSeldon
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Nope, I didnt. Do you know if they have a demo or something like that?

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Old   March 4, 2007, 02:24
Default Re: Best code for Cd calculations?
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Charles
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I don't know. You will have to ask Analytical Methods (http://www.am-inc.com/MSES.shtml) What I do know is that the code is not cheap (US$ 10 000?) , but it is a dedicated method for designing and analysing multi-element 2D sections, even with some transonic flow. As such it is mighty quick, and, from what I've seen, very accurate. Importantly, it uses the same laminar/turbulent transition method as used in XFoil.
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