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A NACA duct,[1] also sometimes called a NACA scoop or NACA inlet, is a common form of low-drag air inlet design, originally developed by the U.S. National Advisory Committee for Aeronautics (NACA), the precursor to NASA, in 1945.[2][3]

Design

Prior submerged inlet experiments showed poor pressure recovery due to the slow-moving boundary layer entering the inlet. The NACA design is believed to work because the combination of the gentle ramp angle and the curvature profile of the walls creates counter-rotating vortices which deflect the boundary layer away from the inlet and draws in the faster moving air, while avoiding the form drag and flow separation that can occur with protruding scoop designs.

Aircraft applications

When properly implemented, a NACA duct allows air to flow into an internal duct, often for cooling purposes, with a minimal disturbance to the flow. The design was originally called a submerged inlet, since it consists of a shallow ramp with curved walls recessed into the exposed surface of a streamlined body, such as an aircraft.

This type of flush inlet generally cannot achieve the larger ram pressures and flow volumes of an external design, and so is rarely used for the jet engine intake application for which it was originally designed, such as the North American YF-93 and Short SB.4 Sherpa. It is commonly used for piston engine and ventilation intakes.

Automobile applications

It is especially favored in racing car design.[4][5] Sports cars featuring prominent NACA ducts include the Ferrari F40, the Lamborghini Countach, the 1996-2002 Dodge Viper, the 1971-1973 Ford Mustang, the 1973 Pontiac GTO, the Porsche 911 GT2, the 1979 Porsche 924 Turbo, and the Nissan S130.

See also

• NACA airfoil
• NACA cowling

References

Further reading

На других языках

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- [en] NACA duct

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[fr] Prise d'air NACA

Une prise d'air NACA (ou entrée d'air NACA, en anglais : NACA duct[1]) est une forme courante de prise d'air ayant une faible traînée, développée à l'origine par le National Advisory Committee for Aeronautics (NACA), le précurseur de la NASA, en 1945[2],[3].

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[it] Presa d'aria NACA

Una presa d'aria NACA,[1] o più propriamente un condotto NACA dall'inglese NACA duct, è un tipo di forma comunemente usata per le prese d'aria che genera una bassa resistenza aerodinamica.

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