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Interpolation of lift and drag coefficients
Hi david , I still have some questions for you.
- If I choose a setup like Figure 1, doesn’t that mean there are 19 elements of blade, 18 control points, and the control points are located at the midpoint position of each blade element. Like figure.2 .
- As shown in Figure 3, if the angle of attack calculated for control point 4 is 25.2 degrees. Does that mean I need to interpolate the airfoil in Cylinder2 to get the coefficient of 25.2 degrees, then interpolate the corresponding coefficients in DU40 and assign them equally to control point 4.
But every time I get values from linear interpolation that are different from what qblade calculates, these are concentrated in airfoils 2-7, while airfoils 1 and 8 correspond to foliations that match. like figure4 . I don’t know why.
Thanks a lot!
BR,
Roby
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Hello Roby,
the interpolation of lift, drag, and other polar data is not performed directly on the aerodynamic panels themselves but rather on the blade object as a whole.
Each panel stores its relative position along the blade and, together with the current angle of attack at the panel, uses this information to interpolate linearly between the polars defined at the blade stations within the blade object.
BR,
David
