The NACA airfoils are airfoil shapes for aircraft wings designed by National Advisory Committee for Aeronautics (NACA). The shape of NACA airfoils is identified by a logical series of digits following the word NACA such as "NACA 2412" . Every digit there signifies the dimensional properties of that airfoil. NACA series extend upto 8-series but the most commonly used are defined by 4-digit, 5-digit and 6-digit series.
NACA 4- Digit Series
In the 4-digit series, every digit tells about the dimension of the airfoil as per the order:
1. - First digit describes maximum camber in percentage of the chord length c = 0.02c
2. - Second digit tells about the location of maximum camber in tenths of chord length c = 0.3c
3. - Last two digits signifies the thickness of airfoil in percentage of chord length c = 0.16c
NACA 5- Digit Series
It has an additional parameter to emphasize for the performance parameter i.e. Lift coefficient, Cl.
1. - 3/2 of first digit in tenths of chord gives the lift coefficient, Cl = 0.3
2. - 1/2 of next two digits gives the location of maximum camber in percentage of chord = 0.15c.
3. - Last two digits tells about thickness of airfoil in percentage of chord = 0.16c.
NACA 6- Digit Series
Contributes in the estimation of minimum pressure at any point on the airfoil and emphasis on maximizing laminar flow.
1. - The number 6 indicates the series.
2. - It describes the location of minimum pressure in tenths of the chord = 0.1c.
3. - The subscript gives the range of Cl in tenths above and below the design Cl in which favorable pressure gradients exist on both surfaces.
4. - It gives the design Cl in 1/10 of chord, Cl = 0.3.
5. - Last two digits indicates thickness in terms of percentage of chord = 0.15c.
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