This turbulent boundary layer interrupts airflow, slows it down, and means the duct in question will have less air moving through it, so the airflow and associated cooling effects to the component beneath will be reduced.

A special duct design, like the NACA duct, is required to channel air into the body of the vehicle without the interference of that pain-in-the-ass turbulent boundary layer, maximizing air-flow performance. Science-savvy folks say that the shallow NACA duct, and its curvature matching the vehicle’s body, deflects the turbulent boundary layer away from the duct’s opening, allowing the faster moving air beneath to slip in with ease. In the context of our tourists, this is like having a special barricade to deflect the clumsy ones out of the way, so that only those moving in a quick, tightly-spaced line could enter the buffet and shovel yummy treats into their slobbering yaps.

Compared to an external ‘scoop’ design, the NACA duct avoids aerodynamic inefficiencies caused by splitting airflow. In extreme cases, thanks to something called flow separation, the airflow at various surfaces of a vehicle’s body (including near a protruding hood scoop) may be virtually still, or even reversed, while fast-moving air slips over top and misses the opening altogether. In the case of our buffet, this amounts to the lineup of tourists approaching the door, becoming confused, and wandering about nearby, but not entering.

Downsides? Because of its design, the NACA duct doesn’t generate much ram pressure, which is why it’s well suited for ventilation and cooling purposes, rather than, say, feeding an air intake where high air pressure is desired.

Neat stuff, yes? Think about it next time you’re looking at a Ferrari, an airplane, or any other NACA duct equipped bit of badass.

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