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Aerodynamic Radial Force

Hi Rob,

I have a question regarding the aeroelastic simulations of a HAWT.

In the aerodynamics blade graph, it’s possible to output normal, tangential, and radial blade forces in N/m, as shown below. “Normal” and “tangential”
directions are defined in relation to the rotor disc, as described in one of your earlier forum posts.
I am wondering how the radial force is calculated. Could you please briefly explain the reason behind the radial aerodynamic force, since generally, in aerodynamics, only normal and tangential forces are addressed?

Best regards,

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Hi Nathan,

generally, a blade can have a 3-dimensional shape (including pre-bend and sweep), as defined in the blade design module. This means that each aerodynamic panel must not necessarily be oriented inside of the rotor plane.

The aerodynamic graphs then show the projection of a blade panels 3d aerodynamic force vector along the tangential, radial and normal direction that is computed for each blade panel. The radial direction is defined as the direction along the normal distance between aerodynamic panel center and the (possibly tilted) rotor axis.

When you look at the force range in the graphs you attached, you see that the radial force is at least one order of manitude smaller than the tangential and normal forces acting on the blade panels. So in most cases, the radial force can simply be considered zero, as in an aeroelastic simulation the axial force along the blade will be dominated by centrifucal forces.



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