• Induced drag is defined as the additional drag force that occurs whenever a moving object redirects the airflow coming at it. This is also called as lift-induced drag, vortex drag or drag due to lift.

• This drag force occurs in planes due to the wings redirecting the air to cause lift and also in race cars with aerofoil wings that redirect the air to cause a downforce and improve traction.

• On a wing with finite span, due to the momentum exchange resulting in a pressure differential between the lower and upper surface of the aerofoil, the air begins to flow from the lower to the upper surface around the wingtip and trailing edge. • Thusproducing vortices along the wingtips and the wings trailing edge.

• The vortices created are unstableresulting ina change of speed and direction of the airflow behind the trailing edge, deflecting it downwards, and thus inducing downwash behind the wing.

• Vortices reduce the effectiveness of the wing to generate lift, thus requiring a higher angle of attack to compensate the lost lift.

• The angular deflection is small and has little effect on the lift. However, there is an increase in the drag equal to the product of the lift force and the angle through which it is deflected.

• Thus, with other parameters remaining the same, induced drag increases as the angle of attack increases.

• High aspect ratio wing produce less induced drag than a wing of low aspect ratio because the size of the wing vortices will be much reduced on a longer and thinner wing