# Reynolds number for Wing analysis

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 January 23, 2013, 23:52 Reynolds number for Wing analysis #1 New Member   Solar Spectrum Join Date: Jan 2013 Posts: 2 Rep Power: 0 hey guys, I would like to know about reynold's number for a wing I have designed a NACA 4412 wing which has wingroot = a , wingtip = b and winglet tip = c (a,b,c are any integers or decimals) please tell me the formula of calculating D for the eqn of reynolds number = VD/ additional info : Wing taper ratio = 0.3 , sweep and sweepback angle = 37 degree altitude = 6000m , density = 0.65970 kg/m3, Pressure = 47182.5 Pa , Temp= 249.2K , velocity of freestream= 100m/s, viscosity= 0.00001594 N sec/m^2

 January 24, 2013, 06:13 #2 Senior Member     Join Date: Jan 2011 Posts: 249 Blog Entries: 5 Rep Power: 17 The definition of Re in this case depends on your purpoces. Do you want to comute Lift, Drag, CM?

January 24, 2013, 12:25
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Solar Spectrum
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Quote:
 Originally Posted by truffaldino The definition of Re in this case depends on your purpoces. Do you want to comute Lift, Drag, CM?
yes, I want to calculate lift and drag for different reynolds number as well as Angle of attack

 January 24, 2013, 12:32 #4 Senior Member   Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,777 Rep Power: 71 your characteristic length "D" is the one that is meaningful for your problem ... any choice of a lenght is coherent with the definition of a Reynolds number, but if you want that the Re number represents the relative magnitude between convective and diffusive fluxes of the momentum quantity for your problem, then you have to choice properly the lenght..

January 24, 2013, 17:28
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Quote:
 Originally Posted by solar.spectrum yes, I want to calculate lift and drag for different reynolds number as well as Angle of attack
What method or sotware are you going to use?

In general, single reynolds number fits only for calculation of 2D airfoil. In your case the analysys should be more sophisticated, unless you are going to have a rough estimation.

Tell us more details.

 January 28, 2013, 10:57 #6 Member   Join Date: Jul 2011 Posts: 42 Rep Power: 14 For a 2D wing (airfoil) you can use your chord length to calculate the value of Re!! If you have a tapered 3D wing then the Re will vary at the different locations. You can however calculate an average Re based on your average chord length. A more in-depth analysis can be obtained at: Fundamentals of Aerodynamics SI by John D. Anderson And/or Aerodynamics for Engineers John J. Bertin, Russell M. Cummings

 January 28, 2013, 11:51 #7 Senior Member   Ali Join Date: Jan 2012 Location: Pakistan Posts: 134 Rep Power: 16 You have to compute the "Mean Aerodynamic Chord" and use that as a characteristics length "D" in Reynolds number formula. The formula for MAC is: MAC = A-(2(A-B)(0.5A+B) / (3(A+B))) here, A : Root chord of the wing and B: Tip chord of the wing This equation for the straight-tapered wing. Hope this solves your problem. Anna Tian, solar.spectrum, Radwanma and 1 others like this. __________________ Best Regards Ali

 July 8, 2015, 11:48 #8 Member   Radwanma Join Date: Oct 2014 Posts: 30 Rep Power: 11 Dear Ali; Can we use the previous equation for a Twisted blade as well? Thanks,

 July 8, 2015, 12:06 #9 Senior Member   Ali Join Date: Jan 2012 Location: Pakistan Posts: 134 Rep Power: 16 Yes. You can. __________________ Best Regards Ali

 Tags aerofoil, wing tip