What is the direction of flow at an angle? What is alpha called? Angle of attack. This
will generate a force which is this straight at the end, its convenient, perpendicular to
direction of flow will we will have lift l, and in the same direction, opposing the flow
will be the drag d. So, l will be lift. You know this know.
So, the, if, if, flow is at angle alpha, then you will generate a flow lift force l
perpendicular to direction of flow and a force opposing the motion which will be the
drag force. Now, this drag, remember, we are talking about inviscid fluid, that is, no
viscosity. This drag would be there due to action of the flow itself without considering
viscous. This is called induced drag. This will be further increased due to viscosity, but
at this moment, we are not talking of viscosity. We are ignoring viscosity. So, we have
this for a span.
flow.