What is lift dependent drag?

So in this post, I will explain the lift dependent drag? And how it is produced.

  • Lift: It is the aerodynamic force, which is perpendicular to the relative wind.
  • Drag: It is the aerodynamic force, which is parallel to the relative wind.

Total drag=profile drag+ induced drag.
Profile drag: is due to aircraft Structure.
Induced drag : Name itself sounds drag produced due to lifting,that means when there is lift, drag will occur due to lifting.


How the lift is generated?
80% of the lift is generated from the wing, due to pressure difference between above and below the wing surface.

How are vortices are formed?
As the air molecules are more below creating more pressure when compared to the top surface of the wing, to equalize this state the below air molecules tend to move above the surface, which results in the formation vortices over the wing.



What are wingtip vortices?
For the wing, the streams of air from above and below the wing are flowing at an angle to each other as they meet at the trailing edge of the wing. they combine to form vortices, when it is viewed from the rear , the rotation is seen the clockwise direction for left-wing, and anti-clockwise direction for right-wing. These vortices try to reach over the wingtip, by the time they reach wingtip, they form large wingtip vortex.
These vortices are visible at the icy conditions.
What is downwash?
The downward part of the vortex acting on the trailing edge of the wing produces a downwash.


Due to this downwash, the lift component gets slightly tilted to back at some angle of attack. this provides induce drag.
Mathematical calculation of induced drag.






  • How to reduce induced drag.

The first thing it can't be completely eliminated as it acts like a byproduct for lift.
Suppose aspect ratio is infinite.then wingtip vortices are decreased, and simultaneously induced drag decreases.
Aspect ratio is the ratio of wingspan to the chord, then the greater the aspect ratio means greater will be wingspan, then greater must be wing strength. again this will lead to the problem to evaluate.






From the above picture, we can see how induced drag varies at a different angle of attack.




Thanks for reading.
Edits , corrections, suggestions are most welcomed.




















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