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Low RE high lift

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Low RE high lift

Old 04-15-2002, 01:50 PM
  #1  
acropilot_ty
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Default Low RE high lift

I have seen wind tunnel testing of several high lift devices at reynolds numbers (under 200,000). One was a 28in span model of a J-3 with full span leading edge slats. The CLmax was around 2.4, but was attained with the entire model at around 30 degrees AOA so that was not the wing alone. The same model was then fitted with a segmented leading edge (similar to the cuffs used on the columbia 300 but alternating to create a series of large vorticies) The segmented leading edge resulted in mild increases to CLmax, but not as high as the leading edge slat. Kruger flaps were also tested, but had little affect on CLmax.

At low reynolds numbers leading edge devices seem to work very well. I believe that it is partly due to transition of the boundary layer to prevent laminar separation. Simple trip strips, and leading edge roughness (sand applied to wind tunnel models) have huge affects at low reynolds numbers, both increasing CL, and lowering CD.

I can see about locating the reports on these and other high lift devices tested in the Embry Riddle wind tunnel, all of the testing here is low reynolds number because of the size of the wind tunnel.

Ty Frisby
Old 04-16-2002, 11:36 AM
  #2  
Tall Paul
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Default wings and structures

I've just completed and flown a Mark Drela design, the E_Allegro_Lite.. Speed 400 direct drive, itty-bitty 6x3 Graupner prop.
Seriously difficult construction, and I even simplified that!
I was surprised to see that this plane is slipperier than the usual glider in its class. It flies faster, but doesn't come down any faster.
Thermals well, turning very tightly without tip stalls.
The airfoil is very skinny, relative to say my Mini-Challenger which is the same general size, but needs a gear-box and 1 more cell to fly well.
And a giant prop.

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