According to potential flow theory, we know that the lift generated by the wings is due to the vortex it creates. In case of a 3D finite wing, there is also a span wise flow due to tip leakage from bottom to upper surface. So if suppose the wing is moving towards left, then the direction of vortex should be clockwise, which in turn should produce an upwash rather than downwash. This should cause an increase in angle of attack rather than decrease.
So the downwash generated should be valid for a wing travelling behind the original wing, but we say that there is downwash on the original wing.
So where is it that I am making a mistake, vortex direction. If yes, what is the correct explanation. Please explain.