Dear Jason,
In many time series of runs with normal and emergency stops I see unreal spikes in e.g. bending moments. For calculation of extreme values these spikes are very annoying. Can you recommend me settings in FAST (e.g. communication intervals for modules) which lead to less unreal peaks in simulation time series?
Thank you for your support.
Best regards,
René
Dear René,
I would not expect you to receive “unreal peaks” in the time-series output from FAST. You’ll have to clarify what problem you are seeing and how you are setting up your simulation.
Best regards,
Dear Jason,
after a stop of the turbine oscillations in moments and deflections are concluding. In FAST the time series looks very well but there is one (or more) time step which steps out of line (spike). During postprocessing the extreme values this faulty time step is disturbing.
So in generall concluding events generate some few time steps out of line wich are “unreal”. Attached you can see those spikes in an example time series.
I hope this will clarify my question.
Best regards,
René
Dear Rene,
Can you clarify what output parameter you are plotting and what features you’ve enabled in your FAST model (modules, aerodynamic options, structural degrees of freedom, controls)?
Best regards,
Dear Jason,
This graph shows the blade edgewise bending moment Mx.
I currently use FAST v8.16 with AeroDyn 15.04 (maybe I have to try it with AeroDyn 14).
I use the modules ElastoDyn, InflowWind, ServoDyn (without TMD), too.
Following settings for the DOFs are used:
---------------------- DEGREES OF FREEDOM -----------------------------------
True FlapDOF1 - First flapwise blade mode DOF (flag)
True FlapDOF2 - Second flapwise blade mode DOF (flag)
True EdgeDOF - First edgewise blade mode DOF (flag)
False TeetDOF - Rotor-teeter DOF (flag) [unused for 3 blades]
False DrTrDOF - Drivetrain rotational-flexibility DOF (flag)
True GenDOF - Generator DOF (flag)
False YawDOF - Yaw DOF (flag)
True TwFADOF1 - First fore-aft tower bending-mode DOF (flag)
True TwFADOF2 - Second fore-aft tower bending-mode DOF (flag)
True TwSSDOF1 - First side-to-side tower bending-mode DOF (flag)
True TwSSDOF2 - Second side-to-side tower bending-mode DOF (flag)
False PtfmSgDOF - Platform horizontal surge translation DOF (flag)
False PtfmSwDOF - Platform horizontal sway translation DOF (flag)
False PtfmHvDOF - Platform vertical heave translation DOF (flag)
False PtfmRDOF - Platform roll tilt rotation DOF (flag)
False PtfmPDOF - Platform pitch tilt rotation DOF (flag)
False PtfmYDOF - Platform yaw rotation DOF (flag)
For AeroDyn 15.04 following settings are used:
1 WakeMod - Type of wake/induction model (switch) {0=n
2 AFAeroMod - Type of blade airfoil aerodynamics model (
1 TwrPotent - Type tower influence on wind based on pote
False TwrShadow – Calculate tower influence on wind based on
True TwrAero - Calculate tower aerodynamic loads? (flag)
False FrozenWake - Assume frozen wake during linearization?
....
2 SkewMod - Type of skewed-wake correction model (swit
True TipLoss - Use the Prandtl tip-loss model? (flag) [us
True HubLoss - Use the Prandtl hub-loss model? (flag) [us
true TanInd - Include tangential induction in BEMT calcu
True AIDrag - Include the drag term in the axial-inducti
True TIDrag - Include the drag term in the tangential-in
"Default" IndToler - Convergence tolerance for BEMT nonlinear s
100 MaxIter - Maximum number of iteration steps (-) [use
Control is a self-written Bladed-style DLL.
Many thanks for your help.
Best regards,
René
Dear René,
I would not expect you to receive spikes in the edgewise bending moment.
I would suggest you try a few things i.e. do the spikes go away if you:
Best regards,
Dear Jason,
Thank you for your suggestions. I will try it.
Best regards,
René
