1. ac

This small program converts any airfoil file in the standard .dat format, to another .dat file including shark nose modification.

The principle used for the conversion is based on defining two zones at the nose of the profile and applying progressive deflections with generic parabolas of degree n.

The first zone includes a segment from the nose of the profile (point (0,0) to a point on the intrados located at a position 1 measured in % of the chord. For the first modification we will add the coordinates of the profile to the coordinates of a generic parabola defined by the function y=k1*x^n1 where the coefficient n1 is chosen by the user (speed of curvature variation) and the coefficient k1 is calculated internally by the program to achieve the maximum deflection defined by the user: k1=deflection/(x1^n1) The second zone to be modified goes from the previous point 1, to a point 3 located further to the right along the intrados. Similarly, for the second modification we will add the coordinates of the profile to the coordinates of a generic parabola defined by the function y=k3*(x3-x)^n3 where the coefficient n3 is chosen by the user (speed of curvature variation) and the coefficient k3 is calculated internally by the program to achieve the maximum deflection defined by the user: k3=deflection/((x3-x1)^n3) It is highly recommended (not mandatory) that the deflection used in zone 1 is exactly the same as that used in zone 2. This way there are no jumps in the modified zones. In some particular cases the designer may be interested in introducing jumps, but in general it will not be necessary or recommended. In addition, a reference point 2 is defined, located between points 1 and 3, so that the inlet of the profile is considered to go from point 1 to point 2. Profile modifications in zone 1-2 are defined in segment 1-3.  If the x-coordinates of points 1, 2, 3 do not exactly match the profile points, the program interpolates the necessary points and adds them to the profile. Therefore, the number of points of the modified profile can be increased by up to 3 points. If the defined deflections are zero, there is no shark nose modification, and the shape of the modified profile is identical to the original, but interpolated points are added if necessary. This can be recommended in case of combining shark nose profiles with normal profiles on the same wing.

2. Use:


There are two versions of the program, the Fortran version and the html version. Both versions are almost identical, except that the fortran version also generates a dxf file with the output file. Both versions generate airfoil-sn.dat files with the modified profile and the input parameters are similar. The html version is perhaps more intuitive and easier to use.

Fortran version:

- Put your standard airfoil.dat file in the working directory (you must use exactly these name airfoil.dat)
- Edit asndata.txt to select shark nose parameters
- Run ./asn.out executable in Linux (or asn.exe in Windows)
- Result file airfoil-sn.dat
- Result file airfoil-sn.dxf

File asndata.txt structure:

real1    real2    real3
real4
real5    real6    real7
real8

Example:

3.0    1.0 1.3
6.0
16.0    1.0 1.3
1.0

Explanation:

Line 1 column 1: real1 (0 to 100 is % of chord first shark nose mofification fron 0% to real1)
Line 1 column 2: real2 (0.0 to 5.0 is % of maximum modification deflection using a generic parabola of the type k1*x^n1
Line 1 column 3: real3 (0.0 to 5.0 is exponent n1 of the generic parabola modification

Line 2 column 1: real4 (end of shark nose inlet in %, init of shark nose inlet is real1)

Line 3 column 1: real5 (0 to 100 is % of chord second shark nose mofification from real1 to real5)
Line 3 column 2: real6 (0.0 to 5.0 usual values is % of maximum modification deflection using a generic parabola of the type k3*(x3-x)^n3
Line 3 column 3: real7 (0.0 to 5.0 usual values is exponent n3 of the generic parabola modification

Line 4: real8 thickness amplification (1.0 is most habitual)

Program generates airfoil-sn.dat and airfoil-sn.dxf file for viewing in CAD.

Run:

Windows64:

asn-win64.exe (double click)

Linux64: ./asn-lin64.out


DXF output file (only Fortran version)


DXF includes interpolation segments by colors. Vertical white lines are ponts 1,2,3. First modification nose to 1 by deflection.
Second modification from 3 to 1 (pont 3 zero deflection, amb point 1 max deflection).



HTML version:

Use in any browser: asn.html There is a button to load the initial .dat profile. The parameters to enter are the same as in the fortran version. Below a graph is generated with the result obtained and there is a button to export the modified profile .dat file with the shark nose. Remember to make the deflections equal in zone 1 (red color) and zone 2 (blue color)






3. Download

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