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ajf
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I have done a lab experiment, to determine the coefficient of lift for an aerofoil, keeping the angle of attack constant.
The equation I have used is
Lift= (1/2) v times v times A times ρ times Coefficient of lLift
v= Velocity of air ρ=air density A= planform area
to give
coefficient of lift = (2 times Lift ) / ( v times v times ρ )
The answers i am getting are confusing me as the coefficient of lift should be constant for differing velocities ( ? or should it vary ? )
Also I think that the maximum coefficient of lift for any aerofoil is about 2.5
The planform area is 145mm by 223mm = 0.0323 square metres
v m/s 3.45, 4.5, 4.8, 5.0, 6.2, 6.5, 7.4
ρ 0.1, 0.13, 0.15, 0.18, 0.21, 0.25, 0.29
Lift ( N) 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8
Coefficient of lift 10.39, 7.05, 7.16, 6.87, 4.6, 4.10, 3.12
the term ρ is a mystery to me. I was reading it directly from an electronic readout, from a pitostatic tube in the wind tunnel.
the electronic readout had a label attached to it which said +-250 P , which i don't understand either - especially when the read out was only 0.1 to 0.29 ?
I am mixed up if it is air density or pressure or what units ρ is.
will you help me make sense of this please.
thanks very much,
ajf
The equation I have used is
Lift= (1/2) v times v times A times ρ times Coefficient of lLift
v= Velocity of air ρ=air density A= planform area
to give
coefficient of lift = (2 times Lift ) / ( v times v times ρ )
The answers i am getting are confusing me as the coefficient of lift should be constant for differing velocities ( ? or should it vary ? )
Also I think that the maximum coefficient of lift for any aerofoil is about 2.5
The planform area is 145mm by 223mm = 0.0323 square metres
v m/s 3.45, 4.5, 4.8, 5.0, 6.2, 6.5, 7.4
ρ 0.1, 0.13, 0.15, 0.18, 0.21, 0.25, 0.29
Lift ( N) 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8
Coefficient of lift 10.39, 7.05, 7.16, 6.87, 4.6, 4.10, 3.12
the term ρ is a mystery to me. I was reading it directly from an electronic readout, from a pitostatic tube in the wind tunnel.
the electronic readout had a label attached to it which said +-250 P , which i don't understand either - especially when the read out was only 0.1 to 0.29 ?
I am mixed up if it is air density or pressure or what units ρ is.
will you help me make sense of this please.
thanks very much,
ajf
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