VORTEX GENERATORS

 VORTEX GENERATORS

Vortex generators have been utilized on most of commercial aircraft. If observed carefully, one can see vortex generators installed at specific locations on Boeing aircraft: for instance, on wing upper surface & on generator applications are shown in the engine nacelles for the B737 & the B767.Some specific examples of vortex generator applications are shown in the accompanying photographs.

These devices have been installed in each case to enhance flying qualities, but each application has its own story. A brief discussion of what vortex generators do is necessary before the design decision

process for specific applications can be discussed. As can be observed from the previous

photographs, these devices are used in assorted sizes and combinations, and can be mounted in

various locations on an airplane. What they all have in common, however, is that they all act like

miniature wings, each creating lift perpendicular to its own surface. By creating lift, they each shed a

downstream vortex which can influence airflow in two distinct ways:

 

(*) The vortex interacts with the boundary layer air on the aircraft surface behind the device by inducing high energy air from outside the boundary layer down to the surface displacing low energy air in the

process as shown in Figure.The air adjacent to the surface is re-energized,and by suitable tailoring of the configuration, the vortex generators can be used to delay, control, or sometimes prevent separation of the boundary layer from the surface. The wing vortex generators installed on the 737, 757 and 767 are applications which take advantage of this mechanism.

(*) The vortex is oriented by appropriate placement of the vortex generator in order to redirect airflow

in the flow field so that adverse interactions are prevented or delayed. With this mechanism, the

generators act as a flow deflector. The large vortex generators installed on the 767 and 737-300

nacelles are examples of applications which take advantage of this mechanism.

Vortex generators have been used to increase aircraft speeds, improve initial buffet boundaries,

improve control authority, and reduce vibrations induced by boundary layer separation on some aircraft. However, these reasons do not explain why vortex generators have been used on the Boeing 737, 757, and 767 aircraft. Vortex generators are used on these aircraft to improve high Mach pitch

characteristics beyond initial buffet and to lower stall speeds in the landing configuration.

 

 To further indicate why vortex generators were used on these latest aircraft, the case history for the
767 is presented to explain why the airplane was configured with wing vortex generators and with the
large vortex generator installed on each engine fan cowl.

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