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Old 1st Dec 2007, 20:18
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delta3
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Pressure Bubble Myth

Induced drag according to the simulator


R44-I, see figure for detailed boundary conditions


IGE (arbritarily choosen as 3ft):





OGE (30 ft):





Remark that the profile drag is (almost) the same, but induced drag is higher in the case of OGE.


So I guess my definitions must be similar to Nick's ones.


d3

PS remark the drag also becomes "induced lift", at small angles this is mostly neglectable


Added defintions according to my doc (is so complicated that even I need to read back!)

2. MAIN ROTOR DRAG

Rotor DM equation (rotor drag small angle approximation used in force calculations for non stalled profile)
In the precise calculations stall is incorporated. The precise and approximate calculations are performed at the end of each simulation to give an idea of approximation errors.

Drag = Profile Drag + Induced Drag
= Drag along IF projected by cos(alfaIF) + Lift by sin(alfaIF)
where cos(alfaIF) is almost= 1 and sin(alfaIF) = alfaIF

and alfaIF is the inflow angle of the relative airflow with respect to the HP plane, that is the plane perpendicular to the rotor axis. Remark that this plane is tilted forward by approximately 3 degrees in the case of the R44.
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