Hello,
I am linearizing with FAST on a two-bladed turbine, and observe following things:
-
If I unlock only the fist flap DOF, I get following eigenfrequencies (in Hz) from the linearized AvgAMat:
0.98458 - blade 1 position
0.98458 - blade 1 velocity
0.98638 - blade 2 position
0.98638 - blade 2 velocity. -
If I unlock the first and the second flap DOF, I get following eigenfrequencies:
0.95432 - blade 1 position
0.95432 - blade 1 velocity
0.95631 - blade 2 position
0.95631 - blade 2 velocity.
2.5812 - blade 1 position (second mode)
2.5812 - blade 1 velocity (second mode)
2.5833 - blade 2 position (second mode)
2.5833 - blade 2 velocity (second mode) -
If I unlock the first two flap DOFs, and the first edge DOF, I get following:
0.94701 - blade 1 position
0.94701 - blade 1 velocity
0.94905 - blade 2 position
0.94905 - blade 2 velocity
1.2851 - blade 1 position (edge)
1.2851 - blade 1 velocity (edge)
1.2864 - blade 2 position (edge)
1.2864 - blade 2 velocity (edge)
2.7014 - blade 1 position (second mode)
2.7014 - blade 1 velocity (second mode)
2.7033 - blade 2 position (second mode)
2.7033 - blade 2 velocity (second mode)
Now, things get strange when I unlock the drivetrain mode, because it breakes the symmetry of the two blades, but only in the edge mode:
-
Drivetrain DOF unlocked ONLY:
1.12 - DT position
1.12 - DT velocity -
Drivetrain DOF and edge DOF unlocked
0.8617 - DT position
0.8617 - DT velocity
1.2817 - blade 1 position (edge)
1.2817 - blade 1 velocity (edge)
4.1722 - blade 2 position (edge) ?!
4.1722 - blade 2 velocity (edge) ?!
Can somebody explain me why this happens?
Thanks in advance,
Mario