Dear Jason,
I have the following questions regarding MBC transformation:
(1) In my understanding, the periodic blade loads can be transformed into the steady loads, namely collective load in x direction, cosine-cyclic load (yawing moment) in y direction, sine-cyclic load (tilt moment) in z direction, correct?
(2) If I want to make the transformation by myself (not MBC3), assuming I have gotten the linearized turbine model (3 blade DOFs, shaft DOF), the shaft loads are already in the non-rotating DOF, so I can just ignore these states in the MBC transformation, correct?
(3) In the MBC transformation, I think the wind disturbances should be wind speeds at 3 blade tips in the rotating frame, and then MBC is applied to the system x.d=A.x+B.u+Bd.ud. However, the FAST linearization list does not provide the wind disturbance at each blade tip, only collective wind speed and vertical shear, etc. So, I guess I should manipulate the state x, controls u (individual pitch) with MBC, and just keep ud still, correct?
Regards,
Xiao
Dear Xiao,
Your understanding of MBC is correct.
Regarding (3), FAST does not include wind disturbances at the blade tips or otherwise in the rotating frame; instead, the wind disturbances in FAST are collective wind speed, direction, shear etc. as you point you. So, you don’t need to apply MBC to the wind-disturbance inputs.
Best regards,
Dear Janson,
Thanks a lot for your reply. So, can I monitor the wind speed at each blade tip, or the wind shear component in FAST simulation?
Thanks,
Xiao
Dear Xiao,
By “monitor”, I assume you are asking if you can output the wind speed at each blade tip or the wind shear from a FAST simulation?
In the AeroDyn v15 module, you can output the ambient wind speeds at any analysis node along the blade (i.e. outputs BαNβVUndx, BαNβVUndy, BαNβVUndz for the undisturbed ambient wind or BαNβVDisx, BαNβVDisy, BαNβVDisz for the ambient wind disturbed by tower-influence effects, if enabled) – see the draft AeroDyn User’s Guide and Theory Manual for more information: nwtc.nrel.gov/system/files/Aero … 15.04a.pdf.
The wind shear is not directly available as an output of FAST, but you can output the ambient wind speed at multiple fixed points in space from the InflowWind module and derive a wind shear from that – see the InflowWind User’s Guide for more information: wind.nrel.gov/nwtc/docs/InflowWind_Manual.pdf.
Best regards,
Dear Jason,
Thanks a lot for your quick reply. I have one more question: are the .fst and other files available for NREL 5MW baseline turbine in FAST v7? Where can I find them?
Regards,
Xiao
Dear Xiao,
FAST v7 models of the NREL 5-MW turbine are available here: wind.nrel.gov/public/jjonkman/NR … Bsline5MW/. We didn’t include the NREL 5-MW models in the FAST archive until the release of FAST v8. I’m not sure why you are using FAST v7, but in most cases I’d recommend an upgrade to FAST v8.
Best regards,
Dear Jason,
I try to run the NREL 5MW baseline turbine in FAST V8, but my controller always receive the errors with negative Vy (there is not such a valid phi value). I understand this may be due to some instability of the controller, but this occurs at the beginning of the simulation, during which the transients cause the problem and it is unavoidable in my opinion. So, should I re-compile the updated AeroDyn 15 and integrate it in FAST v8 to solve this problem?
Regards,
Xiao
Dear Xiao,
Yes, upgrading to AeroDyn v15.04 will solve the problem regarding “no valid value of phi”.
Best regards,