Wikipedia says that because of the area rule's impact on wave drag:
aircraft have to be carefully arranged so that at the location of the wing, the fuselage is narrowed or "waisted", so that the total area doesn't change much.
This much makes sense to me. Though it's a bit difficult to tell, I understand that in the picture supplied there, the green circle toward the front of the aircraft is intended to have roughly the same area as the blue circle and lines through the wing cross-section:
All images from Wikipedia unless otherwise noted
In this image, I can see how the areas through several lines across the fuselage, wings & engines are all intended to be (roughly) equal.
What I don't understand is how this is applied to airliners like the Airbus A380 which they say is:
showing obvious area rule shaping at the wing root
in reference to this image:
To me, it appears that the cross-section at the wing root consists of the same area at the front of the plane (roughly behind the cockpit appears to be where maximum diameter is achieved), plus the area of the wing root, plus the area through the wing, plus the area through a pair of engines (depending on exactly where you make the cross section). As I see it, there's no slimming of the body to make the area through the wing cross section equal to the area of the cross section just behind the cockpit.
This shot from above of another A380 shows that there is no
Coke bottle waist near the wings:
Am I not seeing this correctly, or do I not understand the area rule correctly?