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-   -   Setting Reynolds number in Fluent for plunging airfoil (http://www.cfd-online.com/Forums/fluent/83449-setting-reynolds-number-fluent-plunging-airfoil.html)

 quarkz December 29, 2010 09:56

Setting Reynolds number in Fluent for plunging airfoil

Hi,

I have problems setting the correct Re no. for my simulation.

I want to simulate a plunging airfoil at Re=10000.

Since viscosity of air = 1.7894e-5, density of air=1.225,

Re = u_inf*density*length/viscosity.

So to get Re=10000, I set u_inf=0.17894 m/s

I also set the reference value under the report menu.

My airfoil length is about 1m, which is the reference length.

Is this correct?

Did I miss out anything? My answer is different from some published results.

 fahemsagi January 24, 2011 15:02

Two approaches...

Actually flow is define by Re,Mach and alpha. normally we have certain range of alpha so it is known.
Re and mach number set in fluent must match the Re and mach of the experimenta/published results.
1st case
Mach and chord length is given. then you have to adjust the viscosity to match the required reynolds number
2nd case
for the given reynold number find the density and viscosity from altitude charts and then put these values in reynolds relation to find chord.put this chord in reference values.obviously mach number will be given to you.so you have to change mach in to velocity by multiplying it with acoustic speed corresponding to given reynolds number.

Try it and let me know what happens?
fahemsagi@yahoo.com

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