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I'm teaching an introductory course in fluid dynamics and I'd like to show some "real" data regarding drag and lift forces on an airfoil. It is easy to find data on the geometry of typical airfoils, but I was not so lucky with $C_L = f(airfoil, Re, i)$ and $C_D = f(airfoil, Re, i)$ ($Re$ is the Reynolds number and $i$ the angle of attack). I'm looking for that kind of diagram or data :

Graphs of C_L vs. alpha, and C_L vs. C_D for NACA 4412

Data for commonly known aircraft would be great (B737, B747, A320, A380).

Thanks.

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My first thought was: Abbott-Doenhoff. They wrote a book with lots of measurement data, and you can find it here. Of course, this was all long ago, but public data for the airfoils of today's airliners are not published.

A lot of data is also freely available in old NACA and NASA reports, however, you need to know what data you want to search for it efficiently.

If you want to focus on glider airfoils, the Stuttgarter Profilekatalog would be my next source, but unfortunately there are still people who want to make money from it even though the work was financed with public money. This is also quite old, and more modern airfoils from Delft University are similarly restricted.

Another great source is the UIUC airfoil database, but here the focus is on section data and not on polars. But it contains many useful links with airfoil data.

And then there is always XFOIL: Feed it with the coordinates, and you get very good simulations of what a wind tunnel would measure, at least as long as most of the flow is still attached. Lots of plotting functions will help to uncover what is going on in much more detail than any wind tunnel data could ever hope to do.

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    $\begingroup$ Thanks (+1). Abbott-Doenhoff is a great reference. I was aware of xfoil but I'm still struggling with it since yesterday (it's not that user friendly !). $\endgroup$
    – cjorssen
    Nov 14, 2014 at 15:47
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    $\begingroup$ @cjorssen: XFOIL is at its heart a console application (it was written first in Fortran on a Micro Vax), but it will print out a list of all possible commands when you type "?". Also, the documentation is quite useful. I guess you need to gain a few more days of experience. $\endgroup$
    – Peter Kämpf
    Nov 14, 2014 at 16:05
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I found a web site (mostly in French, but data are language agnostic!). Calculation were made with XFOIL. This is typically what can be found there (with data text file).

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    $\begingroup$ Quite an interesting find! Only a few airfoils look "normal", most are very unusual. The same goes for the choice of Reynolds numbers. A pity that the page has so little background on them. $\endgroup$
    – Peter Kämpf
    Nov 16, 2014 at 18:14
  • $\begingroup$ Is the first graph showing that, for most of the Reynolds numbers, there's a regime where Cd decreases with increasing Cl (assuming that Cx=Cd and Cz=Cl)? That doesn't look right... $\endgroup$
    – Vikki
    Jul 21, 2021 at 16:45
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It’s a text book and as such not quite freely available, but Obert‘s Aerodynamic Design of Transport Aircraft has a lot of surprisingly accurate data (including e.g. 777 drag polars).

Another source: Modelled from independent analysis and maybe not necessarily provable, but there’s some detailed estimates on 787 characteristics published here.

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I think if you try with this site may be you can find a data that you need . http://airfoiltools.com/airfoil/details?airfoil=n0012-il

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While a bit dated with respect to modern transport aircraft, Fluid Dynamic Drag and Fluid Dynamic Lift by S. Hoerner has a ton of data on just about every aspect of interest.

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