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Old   October 12, 2015, 23:38
Smile Getting a Negative Drag_Coefficient
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fangwei
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Hello Everyone

I am running a 2D simulation over a Airfoil via Fluent.

I am getting a good Lift Coefficient, but a negative Drag coefficient.

Is there anyone experiencing the same issues while running the CFD?

Besides, for the initialization method. Is there difference for Hybird and Standard initialization. which one is better?
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Old   October 12, 2015, 23:59
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please check
1) is your mesh fine enogh.
2) is your solution converged.
3) values for force vectors, are they defined correctly for specified AoA.
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Old   October 13, 2015, 00:54
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Quote:
Originally Posted by Bharatt View Post
please check
1) is your mesh fine enogh.
2) is your solution converged.
3) values for force vectors, are they defined correctly for specified AoA.
I think the Mesh is fine, I got a decent Lift_coefficient already

for the (3), what is values for force vector?, for the angle of attack, in the farfield setting, the direction of incoming air is defined based on x, y unit vector component.
for zero AOA, x:1 y:0 right?
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Old   October 13, 2015, 01:15
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yes,
for(drag monitor) specific AoA
X=cos(AoA)
Y=sin(AoA)
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Old   October 13, 2015, 08:00
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Devesh Baghel
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Hi,

Is direction vector correctly defined while calculation of drag ?
sometimes happened, while defining opposite direction of vector which reflects negative value.
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