| > [..] cruised at a slightly higher Mach number, I assumed that was enabled by the center of pressure being moved back a few metres. In high-subsonic cases, it normally points to slightly better aerodynamics in the areas flirting with transonic regimes. The name of the game at those speeds is to try to delay the onset of drag-inducing shocks. These shocks will typically first appear on the wing, or in an area heavily influenced by the wing. In the case of the -300, with the extended bubble coming down at about half the wing root chord, it is possible that the bubble downflow / low-pressure area positively influenced the flow over the wing to slightly delay the transonic onset and further effects. Pulling the bubble further aft made things worse again. > Assuming that the boundary layer is laminar for the entire length of the extended part of the fuselage during cruise Mm. No, I would expect the flow to be turbulent well before that. > and no additional low pressure transition (just one moved back, obviously). Careful where you put your low pressure zones, the wing aerodynamics are critical and sensitive! :-) (see explanation above) But to make things even more interesting, the 747- 300/400/8 cargo all use the short bubble. :-) |