Reynolds number to use

[steven yampolsky]

I am running analysis in Profili and it's asking me about Reynolds numbers. Can anyone help me figure this out. I keep coming up with 500K as the number but in discussions in this section I keep seeing 1000K as the number. Which one is it?

I used the following calculator: http://aero.stanford.edu/StdAtm.html
I  used 80ft/sec speed which is equivalent 55mph which is equivalent to 5.2 second laps with 63 ft lines.
I left 1ft for the chord and tried smaller numbers with little change
I used 1000ft MSL as the altitude.

The calculator gave me 496742.40

Am I doing something wrong or is 500K the right number?

[Tim Wescott]

I get 500K.  I'm using the wing chord as the characteristic length, which I believe is correct.  I'd like to hear from the folks that actually know what they're doing (I don't count) as to whether that's right.

The equation is (density) * (length) * (velocity) / (viscosity).  So it should have a 1:1 correlation with length -- if it doesn't, they've got an error in there.

[Howard Rush]

I sent you both a Reynolds number calculator.

[Tim Wescott]

That was a long way of saying "Yup, about 500K", Howard.

I do love 'merican units.

Although "slugs per cubic foot" seems more an apt way to measure gardens in Seattle vs. Wichita, rather than a measure of air density.

[steven yampolsky]

That's a cool spreadsheet Howard! Thank you! Man, I wish forum owner has enabled spreadsheets as attachments! We could build a library of cool spreadhseets!

[Chuck_Smith]

Don't forget to adjust your results for 3-d flow, or you'll be off on the area calculation.

[Chuck_Smith]

Don't forget to adjust your results for 3-d flow, or you'll be off on the area calculation.

Aspect ratio will affect the lift vs AoA curve for the aircraft.