Mathematical procedure to provide reflex to any profile. Attached
spreadsheet, and theoretical explanation.
It is a very simple geometrical procedure, this is to deform the
back of the profile, raising the trailing edge smoothly, with a
parabolic function, as explained in the figure.
Return to Laboratori
If (X,Y) are the original airfoil coordinates, then the correction in
Y'=Y if X< Xo
Y'=Y + (b/a^2)*(X-Xo)^2 if X >=Xo
where (X',Y') are the new reflexed coordinates
It is very important export coordinates to a .dat file (making
sure the decimal point is "." not ","), and then apply the
function "derotate" and "normalize" with XFLR5 or XFOIL.
The difficulty lies in determining if the resulting profile is
really "good." To do this, we must carefully analyze the
parameters Cl, Cx, Cm with variations in angle of attack,
and compared with other known profiles. Interestingly,
any profile can become slightly or strongly reflex, by applying
this simple transformation.