Low reynolds number flow
What are the equations aplicable in the case of a low reynolds number flow as in the case of a flow past an airplane made of paper

You should solve incompressible NavierStokes

depends upon the problem and your area of interest....
Reynolds Averaged Navier Stroke's Equation(RANS).... is to be the best to catered flow separation 
hi,
i want to calculate the Reynolds number of exhaust gas with a given temperature(°c) and massflow(g/s). What is the fastest way? thanks in advance 
i think as per my knowledge, your flow is compressible and their should be some laminar separation....
the best model to catered that is Menter Transition model of 4 four equations.... 
I'm afraid lowRe # does not imply low mach number.
You can get shock wave for inviscid fluid, where the Re # is zero. Quote:

Quote:
This thread is about aerodynamics of a small (paper) airplane. Have you seen shok waves past paper airplane? BTW, for inviscid fluid RE=infinity 
Hi truffaldino,
my apology... I didn't read it carefully. And you are right, Re # is infinity. hope my advisor is not reading this... Quote:

Hi All,
My opinion that transition model is not necessary in this case. As I understand air flows around paper plane. So velocity is small and we can use incompressible Navier Stokes equation. About turbulence models. I think SA model is good choise in this case. Flow is not very difficult. I am not sure about transition and separation on paper plane. 
I had quite extensive experience with model gliders, they fly at about the same order of RE as paper planes and there is almost always separation and transition there.

Hi truffaldino,
It looks like nice case. It would be interesting to have such model and experiment results. Could you provide it. Thanks 
Hi Vasiliy,
Information about low reynolds number airfoil design and its peculiarities (due to separation/transition bubbles) is quite extensive and easily acessible over the web. As an example you could take a look at Martin Heppelere website, and in particular http://www.mhaerotools.de/airfoils/ Data on very slow airfoils for Discus Launch Gliders (down to RE=40K) can be found here http://www.charlesriverrc.org/articl...tairfoils.htm People from RC glider commmunity mainly use Mark Drela's xfoil and also XFLR5 software. These are nice programs that are free and increadibly easy to use: Xfoil analyses airfoils, while XFLR5 analyses an airplane as a whole. These programs are based on viscousinviscid interaction method with boundary layer integral methods. They use e^n transition model and some turbulence model. One can also have a rough idea about presence of separation at low Re for 2D airfoils even without using the above software: one can use Thwaites integral BL method. It is very simple and takes a couple of hours to write a program in mathlab or maple. About experimental data: there has been an extencive testing by UIUC Applied Aerodynamics group, and measured polars were available free of charge on the web. Now they are selling them as reference books: see e.g. http://www.ae.illinois.edu/mselig/uiuc_lsat.html but some of them are still scattered over the internet free of charge Truffaldino 
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