FAST theory manual

Dear Dr. Jason,

I would like also to receive the Unofficial FAST theory manual if possible.

My email: amrmetwally@riam.kyushu-u.ac.jp

Thank you so much.

Best regards,
Amr Ismaiel

Sent.

Dear Dr. Jason,

Could you please send me the Unofficial FAST theory manual.

My email: sarkars@tcd.ie

Thank you so much.

Sent.

Dear Dr. Jonkman,

Could you also send me the “Unofficial FAST Theory Manual” for FAST v7,v8 and user’s guide for FAST v8?

My mail address: abc720919@gmail.com

Thank you

Kind Regards
Jason. Lai

Sent.

The following constitutes the current User’s Guide for FAST v8:

Best regards,

Dear Jason,

Could you please send me the Unofficial FAST theory manual? My email is zhoushengtao1991@foxmail.com

Thank you!

Best regards,
Shengtao Zhou

Sent.

Could you please send me the Unofficial FAST theory manual?

My email is gerrykoun@gmail.com

Thank you in advance

Sent.

Dear Dr. Jonkman

In the Unofficial FAST Theory Manual, in the Kinetics document, the Nacelle inertia dyadic has terms only parallel to d2 unit vector. Can you please clarify why the terms parallel to d1 and d3 unit vectors neglected? Here I’m assuming that d1, d2 & d3 are also the principal axes for the Nacelle.

I have attached the page below. I have also observed the same for generator inertia where Generator Inertia dyadic only has terms parallel to c1.

1.pdf (70.2 KB)

Thank you,
Saptarshi

Dear Saptarshi,

Good question. Yes, your understanding is correct. The pitch/roll inertias of the nacelle and the transverse inertias of the generator are neglected in ElastoDyn under the assumption that there influence on the full-system dynamic response is small relative to other terms. It would not be too difficult to modify the source code to include the currently neglected terms to see if they have an influence on your system.

Best regards,

Dear Dr. Jonkman,

Thanks a million for the clarification. The FAST input file has the nacelle inertia value about the yaw axis. From where can I get the nacelle inertia values about the other axes? Or should I just calculate it from the nacelle dimension?

Thank you,
Saptarshi

Dear Saptarshi,

You’d have to get that using data available for the turbine you are modeling.

Best regards,

Respected Dr. Jonkman,

I was going through the Drivetrain modeling from “Unofficial FAST theory manual”. There is a term T^{Gen} used which represents a positive load extracted. This quantity is represented as a function of Gear Box Ratio x Angular speed and time. So, for a wind turbine of with constant power output of 5MW can this quantity be represented as:

T^{Gen} = 5MW/GBRatio/LSSTipVxa(in rad/s).

Thank you,
Saptarshi

Dear Saptarshi,

T^Gen in the “Unofficial FAST Theory Manual” is a variable that refers to the generator torque computed by the generator or torque-controller models.

Your equation likely applies under steady-state conditions, except that it is missing possible effects from gearbox efficiency/friction (which reduces the torque in the high-speed shaft relative to the low-speed shaft) and generator efficiency (which means that more than 5-MW of mechanical power are needed to generate 5-MW of electrical power). Under transient conditions, the equation will depend on the generator or torque-controller settings.

I hope that helps.

Dear Dr. Jonkman,

In FAST, for aeroelastic simulation the blade velocities in which reference frame are returned to AeroDyn? Also, are the returned velocities calculated from the hub (i.e. HvS1(r)) or are they calculated in the inertial reference frame (i.e. EvS1(r))?

Thank you,
Saptarshi

Dear Saptarshi,

In FAST, all positions and velocities transferred to AeroDyn are expressed in the inertia frame coordinate system.

I hope that helps.

Best regards,

Dear Dr, Jonkman,

Due to the mode shapes of the blades the cross flapwise blade stiffness between mode 1 and 2 (k12_B1F1) that I’m calculating is coming out as negative. Do you remember if this is the case and the same is also used in FAST or not?

Is there a way to extract the structural modal stiffness or frequencies from FAST?

Thank you,
Saptarshi

Dear Saptarshi,

I would expect a quite small cross-stiffness term between the first and second flapwise-bending modes of the blades (only nonzero if the mode shapes are not orthogonal).

Yes, you can extract the full-system mass, stiffness, and damping matrices, as well as the full-system natural frequencies through a FAST linearization analysis.

Best regards,