From Wikipedia, the free encyclopedia
Jet air inlet design
Concept picture of a submerged inlet for a jet aircraft
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
[
edit
]
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
[
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]
Three intakes (facing right) on an engine
cowling
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 greater 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
[
edit
]
The
Ferrari F40
sports car has "NACA style" side and
hood scoops
.
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
. It is also prevalent in some motorcycle designs, such as the 1994?1997
Honda VFR750F
or the 1994-1998
Ducati 916
.
See also
[
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]
References
[
edit
]
Further reading
[
edit
]
Wikimedia Commons has media related to
NACA ducts
.