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.
Related Documents

Hot Air Balloons  Calculate the Lifting Force
Calculate hot air ballon lifting force.