BModes flp_iner


I’m try to model a tower in BModes and got now a problem by setting up the section properties input file.
To be more specific, I don’t understand the parameters flp_iner and edge_iner.
Can someone maybe explain how to compute for a constant cylinder section the two section properties for flp_iner and edge_iner.
I would use the following expression to compute flp_iner.


The problem is how to be able to compute the moment of inertia per unit length if the length (h) of the section is squared.

Thanks for your help.

Best regards,


Dear Matthias,

In BModes, the cross-sectional flapwise mass inertia, flp_iner, should be computed as the integral of the mass density times the square of the flapwise distance from the blade section mass center to the differential area element over the cross-sectional area of the section. That is, flp_iner = ∫∫ ρ(x, y)x^2dxdy, where ρ(x, y) is the mass density in kg/m^3 and x and y are the flapwise and edgewise distances in meters from the blade section mass center to the differential area element, respectively. Likewise, edge_iner should be computed using the edgewise distance: edge_iner = ∫∫ ρ(x, y)y^2dxdy.

For a solid cylindrical cross section of uniform density ρ and radius r, flp_iner = edge_iner = ρπr^4/4.

Best regards,