Lift and Drag
Lift and drag forces acting on a body like an air foil in a fluid flow.
Lifting Force
The lifting force acting on a body in a fluid flow can be calculated
F _{ L } = c _{ L } 1/2 ρ v^{2}A (1)
where
F _{ L } = lifting force (N)
c _{ L } = lifting coefficient
ρ = density of fluid (kg/m^{3} )
v = flow velocity (m/s)
A = body area (m^{2})
Drag Force
The drag force acting on a body in fluid flow can be calculated
F _{ D } = c _{ D } 1/2 ρ v^{2}A (2)
where
F _{ D } = drag force (N)
c _{ D } = drag coefficient
ρ = density of fluid (kg/m^{3} )
v = flow velocity (m/s)
A = body area (m ^{ 2 > } )
Required Thrust Power to overcome Drag Force
The thrust power required to overcome the drag force can be calculated
P = F _{ D } v (3)
where
P = power (W)
Example  Aeroplane and Airfoil Lift  Drag and required Thrust Power
For an aeroplane with velocity 100 m/s , wing area 20 m^{2}, a drag coefficient 0.06 and a lift coefficient 0.7  the lifting force acting on the airfoil can be calculated
F _{ L } = 0.7 1/2 (1.2 kg/m^{3} ) (100 m/s)^{2}(20 m^{2})
= 84000 (N)
= 84 (kN)
The drag force can be calculated
F _{ D } = 0.06 1/2 ( 1.2 kg/m^{3} ) (100 m/s) ^{ 2 } (20 m^{2})
= 7200 (N)
= 7.2 (kN)
Required thrust power to overcome the drag force:
P = (7200 N) (100 m/s)
= 720000 (W)
= 720 (kW)
Related Topics

Fluid Mechanics
The study of fluids  liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
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