What is XFoil and How Does it Aid in Airfoil Design Research?

[rm446]

Does anyone know of any types of research out there that attempts to establish analytical ways to design an airfoil. As far as I understand it right now, when someone wants to design an airplane they grab some premade airfoil shapes and test there design empirically using CFD or a wind tunnel. What I'm interested in is finding a way to take a set of fluid properties and aircraft requirements and generate an aerodynamic shape that'd yield the desired properties.

Does anyone know the name of any research like that? (Or any Universities/Professors that do this type of research?)

 

[boneh3ad]

Every major airframer does this with new plane designs and many researchers do it as a precursor to their projects.

It is a big enough job to require trained people from both experimental and computational backgrounds a fair amount of time to do it. It isn't big enough to be the sole research thrust of any professors/groups that I know of except maybe a few small groups within the airframers.

 

[Pkruse]

I've floated more than 120 tons on a similar device. They are available commercial off the shelf and are used for industrial applications. But it took more than a million dollars of engineering and shop time to make it work. I agree with Boneh3ad on this one.

But if you want to know more, go Google "air bearings." Small systems like yours might work on the scale of a home project. These work on compressed air. Once you figure out the air flow and pressure you need, then you can size your compressor and engine.

 

[RandomGuy88]

This is essentially inverse airfoil design. The designer prescribes various desired properties such as the velocity/pressure distribution, boundary layer development, thickness, pitching moment... And then the airfoil is designed to provide the desired characteristics generally using a conformal mapping technique. You should look up the work of Professor Michael Selig.

 

[AIR&SPACE]

Well, for analytic methods there's thin airfoil theory which was developed in the 1920s by Munk, Glauert and others. TAT allows for predicting the angle of zero lift, the lift slope and the moments coefficients. Coupled with the new theory of stall onset provided by Prof. Wallace Morris (http://dx.doi.org/10.1115/1.4005101) a full lift polar can be analytically approximated.

 

[RandomGuy88]

Thin airfoil theory is not a design tool though. Its not even a very useful analysis tool. Inverse design methods are what the OP is looking for.

 

[AIR&SPACE]

I would say that TAT is a useful tool, even if only used qualitatively. It provides a good approximation of properties and geometric effects on lift and requires much less expertise than a CFD analysis. In the OP's words, "attempts to establish analytical ways to design an airfoil." TAT can be used as the basis for inverse design methods and certainly at least attempts to provide an analytical means by which to design an airfoil.

One method for airfoil design in non-lifting, transonic flight is explored in "Transonic Small-Disturbance Theory - A Tool for Aerodynamic Analysis and Design" by Zvi Rusak and Jang-Chang Lee.

 

[boneh3ad]

I would say that TAT is a useful tool, even if only used qualitatively.

It was useful when designing planes like the P-51 perhaps. Today, not so much. Thin airfoil theory (or small disturbance theory if you prefer that terminology) is really more useful these days as an illustrative tool to help illustrate some general properties of airfoils. As a design tool it has been rendered long since obsolete for most purposes.

 

[AIR&SPACE]

Absolutely agree. The OP asked for what analytical methods existed and who, if anyone exists, still conducts research on analytical methods. It's the same as someone asking about genetics and being referred to a Punnett square. Yes, there's more to it, but it covers the basic idea.

 

[Aero51]

You are looking for something which i have been researching in my freetime for the past 2 years: a formula for the aerodynamic coefficients as a function of Re,M, and the curvature of the body. There is no formula. Everything is done with CFD and guessing. The Eppler series for instance was generated using conformal mapping techniques.

 

[HowlerMonkey]

I've been trying to find information on the J2M concerning it's airfoil which is listed as "laminar flow" but is not represented by a naca number.

 

[Aero51]

Naca Airfoils are not necessary laminar. If you are looking for specifically designed laminar airfoils look for the NLF (Natural Laminar Flow) designation.

 

[boneh3ad]

There is no reason why a J2M would have a NACA designation given the fact that it was a Japanese design at a time when Japan and the US were not exactly on speaking terms. It is the same reason you won't find a NACA number for something like an Me 262 or a Ju 88 or any other axis-designed aircraft.

Why exactly are you trying to find this airfoil.

 

[HowlerMonkey]

Because I do aerodynamic testing at NASA, rebuild warbirds for the smithsonian, and I was curious because this is one of the few planes we don't have.

There is test data from freeman field but not much detail on the wing has been published.

Never mind guys...I'll just visit chino and measure it.

As far as Axis planes not having naca numbers...that is not true.

There are plenty of axis airfoils that influenced the west.

Some were assigned NACA numbers, but not the J2M.

 

[Aero51]

Have you checked the UIUC database? You may want to email professor selig.

 

[Mithrandir13]

XFoil is an example of software developed by Dr. Mark Drela of MIT.

http://web.mit.edu/drela/Public/web/xfoil/

you can work "Backwards" with this application stipulating pressure coefficients and outputting the section geometry...

as well as taking existing sections that might be close and tweaking'em to get a more specialized section