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Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Mar 10, 2018 9:12 am
by Ali.Elyaakoubi
I found in some articles the model os refered as" NREL's 5MW Benchmarking WT''

Can you please tell me what about this nomination

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Mar 10, 2018 10:12 am
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Tue Mar 13, 2018 5:25 pm
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Tue Mar 13, 2018 8:37 pm
by Jason.Jonkman
Dear Ali,

See the following FAQ for guidance on selecting a time step for FAST v7: http://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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Fri Mar 16, 2018 3:44 pm
by Ali.Elyaakoubi
Thank you so much


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


Sincerely yours

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Fri Mar 16, 2018 4:52 pm
by Jason.Jonkman
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: https://nwtc.nrel.gov/system/files/FAST.pdf (pages 12-14 and Figures 17-19).

Best regards,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Mar 17, 2018 7:59 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Mon Mar 19, 2018 9:09 am
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Mon Mar 19, 2018 9:27 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Mon Mar 19, 2018 12:06 pm
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Mar 21, 2018 12:27 pm
by Ali.Elyaakoubi
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)

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Mar 21, 2018 1:22 pm
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Mar 21, 2018 4:08 pm
by Ali.Elyaakoubi
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?

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Mar 21, 2018 4:43 pm
by Jason.Jonkman
Dear Ali,

Please see the following forum topic for more information on the theory basis of the ElastoDyn module of FAST: viewtopic.php?f=4&t=424. Of course, FAST has other structural modules e.g. BeamDyn for advanced blade dynamics and SubDyn for substructures.

Best regards,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Mar 21, 2018 5:40 pm
by Ali.Elyaakoubi
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