Hi, I´m dealing with 2d airfoils with and without flaps and slats. Fluent doesn´t 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!

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

Hi buch, Yes, I tried all what you said (all kind of meshes, different turb models, etc) Right now I´m using Fluent, and I heard that others codes use differents approaches to calculate the Cd with better results than Fluent.

I´ll keep trying! Thanks

Have you tried MSES?

Nope, I didn´t. Do you know if they have a demo or something like that?

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.