There Are Holes in this Airplane

Boeing adds miniscule holes to make the 777X more efficient:

Boeing’s new 777X is getting a lot of attention for its composite wing with folding tips and its super-efficient engines, but one of the airliner’s most innovative features are the tiny holes in its tail that smooth airflow and improve fuel efficiency.
The holes help smooth airflow around the tail by improving something called laminar flow, basically making the airplane more aerodynamic, which reduces fuel consumption. “Aerodynamic advances such as a hybrid laminar flow control vertical tail,” are the few words Boeing used to describe it in a press release announcing the 777X, Boeing’s impressive updating of its long-range twin-engine airliner. Boeing is working with NASA to further develop the idea to include “sweeping jet actuators” embedded in the tail of future models. Such advancements in airflow manipulation could bring significant fuel savings.
Laminar flow occurs when when air flows smoothly over a surface. Think of a water flowing smoothly around a large, smooth round rock. The water flows easily, and the water appears glassy. But if the rock is jagged or the water is flowing fast enough, turbulent eddies form. The same thing happens at the micro scale as an airplane moves through the air, and that turbulent flow increases drag. Increased drag leads to increased fuel consumption.
The challenge is that laminar flow is difficult to maintain over the entire surface of a wing or tail. As the air flows past the leading edge, it becomes more turbulent, separating from the surface and increasing drag.
Boeing has come up with an innovative solution with its hybrid laminar flow control system, but is keeping most of the details under wraps. The company is using a similar innovation on the 787-9, the stretched version of the Dreamliner, providing a few clues. Tiny holes covering the unpainted leading edge of the 787-9′s vertical tail are used to control the airflow over the surface (the leading edge of the vertical tail on the 777X in the artist rendition at top is also unpainted). Turbulent airflow is reduced through suction as air pulls the turbulent layer through the small holes. This technique has been researched for decades (.pdf), including research by NASA on the F-16XL and more recently by Boeing rival Airbus on an A320 test aircraft in the late 1990s. By ingesting the turbulent layer of air through the tiny holes, the overall drag over the tail surface is reduced.

Interesting. Talk of laminar flow puts me back in fluids lab.