NREL 5MW Blade Eigenfrequencies with Bmodes

Hi to all, I’m Ivano Quarta and i’m new to this forum. I’m using 5MW NREL model to compare two different aeroelastic codes. For this reason i would like to get the natural frequencies of blade and tower using Bmodes.
Reading the document http://www.nrel.gov/docs/fy08osti/42250.pdf I understand that there is two way to obtain uncoupled modes of Blade: decoupling the flexural problem from the torsional one, or considering the modal participation of the single mode.

With the fist way i got the following results obtained eliminating the inertia and cg offset and increasing the axial and torsional stiffness (see the attachment):

Mode Bmodes Calc err % 1 0.69584 0.66696 4.15% 2 1.17550 1.08420 7.77% 3 1.95960 1.88500 3.81% 4 4.04710 3.95923 2.17% 5 4.56570 4.23554 7.23% 6 8.14450 7.03750 13.59%

I think the difference is due to a partial coupling of modes (for example, the first flap mode have a little partecipation of the edge).
How i can risolve this mismatch?
Which method has been used in the document to derive the frequency of the mode with greater participation?

Thank you very much. I am appreciated your help.
Bmodes.xlsx (177 KB)

Solved! Reading another post i set the twist angle to zero to uncouple flap and edge modes. I also change some parameters to my model and results match.

Mode Bmodes Calc err % 1 0.67639 0.67289 0.52% 2 1.08970 1.08429 0.50% 3 1.94890 1.95460 -0.29% 4 4.04300 4.00517 0.94% 5 4.51440 4.54865 -0.76% 6 8.10160 8.22479 -1.52% 7 9.3866 9.35616 0.32% 8 12.747 12.50460 1.90% 9 17.157 16.88141 1.61% 10 18.54 18.22292 1.71%