Dear Arsalan,
OK, I’m able to reproduce your results.
I noticed that the KBBt and MBBt matrices written by SubDyn are quite different between these models. It sounds like you’ve changed the apparent fixity length, but can you clarify what you changed? Are you expecting such large differences in KBBt and MBBt?
When I run BModes with the original KBBt and MBBt matrices (i.e. the original hydro_K and hydro_M matrices from BModes.txt from AeroDyn Feedback), the BModes output is much clearer, where I would conclude the following:
Mode 1 - freq=0.309 Hz; 1st tower side-to-side
Mode 2 - freq=0.312 Hz; 1st tower fore-aft
Mode 6 - freq=2.278 Hz; 2nd tower side-to-side
Mode 7 - freq=2.729 Hz; 2nd tower fore-aft
I would conclude the same mode # identification from 26mBModesout.txt (with different frequencies), but I’m not sure why the side-to-side deflection does not exceed the fore-aft deflection in mode 1 in this case.
Best regards,