7 Flight Mystery and Aerodynamic Principles
543
Fig. 7.136 A350 landing gear puts down
Fig. 7.137 B787 landing gear puts down
gear are important sources for the aerodynamic noise. For the leading edge
slats, the shed trailing edge vortex and the unstable impulse in the groove
area are the main noise sources. The unstable impulse includes the interaction between the vortex in the shear layer, and the interaction between the
vortex and the solid wall in the recirculation zone and the reattachment zone
(as shown in Figs. 7.141 and 7.142). For the trailing edge flap, when the flaps
are open, due to the sudden change in the spanwise lift, a strong vortex is
generated at the side edges of the flaps, including high-frequency small-scale
unstable vortices and low-frequency large-scale vortices. These two different
543
Fig. 7.136 A350 landing gear puts down
Fig. 7.137 B787 landing gear puts down
gear are important sources for the aerodynamic noise. For the leading edge
slats, the shed trailing edge vortex and the unstable impulse in the groove
area are the main noise sources. The unstable impulse includes the interaction between the vortex in the shear layer, and the interaction between the
vortex and the solid wall in the recirculation zone and the reattachment zone
(as shown in Figs. 7.141 and 7.142). For the trailing edge flap, when the flaps
are open, due to the sudden change in the spanwise lift, a strong vortex is
generated at the side edges of the flaps, including high-frequency small-scale
unstable vortices and low-frequency large-scale vortices. These two different