Lift and drag
From CFD-Wiki
The force on a body immersed in a fluid is decomposed into lift and drag. Lift is the component of the force normal to the freestream velocity while drag is the force in the direction of the freestream velocity.
The force on a body can be obtained by integrating the stress on the surface of the body and is given by
where
- is the total stress
- is the static pressure
- is the shear stress
- is the unit normal vector to
If is the freestream velocity with then the drag force () is given by
The remaining force can be considered as lift force. For a 3-D slender body the lift force may be broken into a normal force and a side force.
In 2-D, the lift () and drag are given by
where is the angle of attack, that is the angle between the freestream velocity and the axis.