# Aerospace Urgent help: reynolds number for wing

1. Jan 23, 2013

### solar.spectrum

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 = ρVD/μ

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

2. Jan 24, 2013

### RandomGuy88

For a wing the length scale for the Reynolds number is typically the mean aerodynamic chord of the wing.

http://en.wikipedia.org/wiki/Chord_(aircraft)#Mean_aerodynamic_chord

however you can also use the root chord or the tip chord or any thing in between really. The choice depends on what you are interested in. However the convention for a wing is the mean aerodynamic chord so I am assuming that is probably what you want.