Dear Mr Jason

I hope you are well

Tell me please why are you called the NREL’s 5MW WT as a benchmarking model

As well as the torque and GSPI why are you called they as reference controllers

As I know the word benchmarking must verify somes standard norms,which norms have benn verifyed by this model and their controllers

Sincerely yours

Dear Ali,

I’m sorry, but I’m not sure I understand your question.

I typically use the word “baseline” to refer to the specified NREL 5-MW turbine and its controller. I use the word “baseline” to distinguish from further developments/improvements by others.

Best regards,

I found in some articles the model os refered as" NREL’s 5MW Benchmarking WT’’

Can you please tell me what about this nomination

Dear Ali,

I’m not sure. Perhaps the term “benchmarking” is used because the NREL 5-MW baseline wind turbine has been used a lot in benchmarking exercises e.g. the IEA Wind Task 23 and Task 30 Offshore Code Comparison Collaboration (OC3), OC3 Continued (OC4), and OC4 plus Correlation (OC5) projects?

Best regards,

Thank you for your reply

Tell me again on how are you based to choose the step time of integration DT 0.0125 s

Sincerely yours

Dear Ali,

See the following FAQ for guidance on selecting a time step for FAST v7: wind.nrel.gov/designcodes/FAQ.html#FASTTimeStep. (FAST v8 has some further numerical options, but the FAQ still applies to ElastoDyn and AeroDyn.)

Best regards,

Thank you so much

Please explain me what about the two DOF the rotor tail furl

Sincerely yours

Dear Ali,

The rotor- and tail-furling degrees of freedom in FAST v7 are explained in the Model Description section of the old FAST User’s Guide: nwtc.nrel.gov/system/files/FAST.pdf (pages 12-14 and Figures 17-19).

Best regards,

Tell me if furling-Tail represent the blades rotations away from the direction of the wind, either horizontally or vertically.

And tell me also what is the difference between them and the yaw roation

I want also to know Mr jason if the flap-wise bending moment at the root of the pales is the moment at the tip or at the level of hub

" In FAST each blade is modelled by 3 DOFS flap-wise deflexion as well as torsion and the edge-wise deflexion". I have found also other nomination ‘’ Each blade is modelled by 3 DOFS which are the first and second flap-wise and the first edge-wise modes". Can you please confirm or explain these sentences and what is the relations between them

Sincerely yours

Dear Ali,

Yes, either rotor- or tail-furling will result in the rotor skewing out of the primary wind direction to reduce thrust, power, etc. The difference between furling and yawing is the location/orientation of the hinge; also, furling is typically passive whereas yawing is often actively controlled.

I’m sorry, but I don’t understand your question about the flapwise moment.

I’m not sure where these sentences came from, but only the second one is correct for the ElastoDyn module of FAST: “Each blade is modelled by 3 DOFS which are the first and second flap-wise and the first edge-wise modes.”

Best regards,

Thank you very much Mr Jason

I meant what represent the “flap-wise bending moment at the root of the blades”. Normally the moment is always calculated according an point, tell me at which point is calculated this moment in the figure attached

Dear Ali,

The ElastoDyn module of FAST will calculate the blade-root loads about the point where the blade-pitch axis intersects with the blade root plane. Normally this point would be at the center of the pitch bearing, but the “root” location in the numerical FAST model is really up to who put the FAST model together.

Best regards,

Mr Jason

Thank you for your reply

I have found in litterature that the WT may be modelled from one to sex MASS model

I have found that in FAST the drive train is two mass model (2DOFs) in addition 9 DOFs of the blades. If we take the sex mass model we found the blades are modelled by 3 inertia, hub one, gerabox one and the generator one.

Can you please explain me what is the relation between the modelisation by mass ( 3, 6 mass) and the modelisation by DOFs (24 DOFS)

Dear Ali,

I’m not familiar with the 6-mass model you are referring to. Is this a model composed of 6 rigid bodies and 6 rotational joints?

Best regards,

On which model is based FAST. I found it is based on the modularization , can we said that the components of the WT is modelled as bodies linked with DOFs?

Dear Ali,

Please see the following forum topic for more information on the theory basis of the ElastoDyn module of FAST: http://forums.nrel.gov/t/coupled-blade-modes-in-fast/314/1. Of course, FAST has other structural modules e.g. BeamDyn for advanced blade dynamics and SubDyn for substructures.

Best regards,

Thank you for your reply

A simple aking, when we said the first and second flap-wise mode, tel me if it means the bending and its derivative, or what

Dear Ali,

The first and second flapwise modes are the first two bending modes of the blade (associated with the first and second natural frequencies, respectively).

Best regards,

Sorry for my multiples asking, but my thesis is based on this code AND I nedded to know these details

Tel me again if some structures of the code are based on finite element method, or what position of this method in this simulateur

Sincerely yours

Dear Ali,

The SubDyn module of FAST is based on a linear beam finite-element approach and the BeamDyn module of FAST is based on a nonlinear beam finite-element approach. I wouldn’t call the ElastoDyn module a finite-element approach, although the tower and blades are similar to a finite-element approach in that shape functions (in this case mode shapes) are used to form generalized mass, stiffness, and damping matrices (and geometric nonlinear terms as well). However–as described in the forum topic I linked above: http://forums.nrel.gov/t/coupled-blade-modes-in-fast/314/1 --ElastoDyn employs a combined modal and multibody dynamics formulation.

Best regards,