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A NACA duct, 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.
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
It is especially favored in
A NACA duct, 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
The National Advisory Committee for Aeronautics (NACA) was a United States federal agency that was founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its ...
(NACA), the precursor to NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
, in 1945.
Design
Prior submerged inlet experiments showed poor pressure recovery due to the slow-movingboundary layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a Boundary (thermodynamic), bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces ...
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
In fluid dynamics, flow separation or boundary layer separation is the detachment of a boundary layer from a surface into a wake.
A boundary layer exists whenever there is relative movement between a fluid and a solid surface with viscous fo ...
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
An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...
.
This type of flush inlet generally cannot achieve the greater ram pressures and flow volumes of an external design, and so is rarely used for the jet engine
A jet engine is a type of reaction engine, discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include Rocket engine, rocket, Pump-jet, water jet, and ...
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
Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. In North America, the term is commonly used to describe all forms of automobile sport including ...
design. (Practical guidance on designing and building NACA ducts for motor-racing applications) Sports car
A sports car is a type of automobile that is designed with an emphasis on dynamic performance, such as Automobile handling, handling, acceleration, top speed, the thrill of driving, and Auto racing, racing capability. Sports cars originated in ...
s featuring prominent NACA ducts include the Ferrari F40
The Ferrari F40 (Type F120) is a Rear mid-engine, rear-wheel-drive layout, mid-engine, rear-wheel drive sports car engineered by Nicola Materazzi with styling by Pininfarina. It was built from 1987 until 1992, with the LM and GTE race car version ...
, the Lamborghini Countach
The Lamborghini Countach ( ) is a rear mid-engine, rear-wheel-drive layout, rear mid-engine, rear-wheel-drive sports car produced by the Italian automobile manufacturer Lamborghini from 1974 until 1990. It is one of the many exotic designs dev ...
, the 1996–2002 Dodge Viper
The Dodge Viper is a sports car that was manufactured by Dodge (by Street & Racing Technology, SRT for 2013 and 2014), a division of American car manufacturer Chrysler from 1992 until 2017, having taken a brief hiatus in 2007 and from 2011 to 20 ...
, the 1971–1973 Ford Mustang
The Ford Mustang is a series of American Car, automobiles manufactured by Ford Motor Company, Ford. In continuous production since 1964, the Mustang is currently the longest-produced Ford car nameplate. Currently in its Ford Mustang (seventh ...
, the 1973 Pontiac GTO, the 1979 Porsche 924 Turbo, the Maserati Biturbo, the Nissan S130, and the Porsche 911 GT2. It is also prevalent in some motorcycle designs, such as the 1994–1997 Honda VFR750F or the 1994-1998 Ducati 916.
See also
*NACA airfoil
The NACA airfoil series is a set of standardized airfoil shapes developed by this agency, which became widely used in the design of aircraft wings.
Origins
NACA initially developed the numbered airfoil system which was further refined by the Un ...
* NACA cowling
The NACA cowling is a type of aerodynamic Aircraft fairing, fairing used to streamliner, streamline radial engines installed on airplanes. It was developed by Fred Weick of the National Advisory Committee for Aeronautics (NACA) in 1927. It was a ...
References
Further reading
* * {{refend Aircraft aerodynamics Engine technology Duct