FAST

Provide feedback, request enhancements, and get help with wind-turbine computer-aided engineering tools.

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JoseManuel.Ezquerra
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Joined: Mon Apr 04, 2011 1:11 am
Organization: Ikerlan
Location: Spain

FAST

Postby JoseManuel.Ezquerra » Wed Apr 06, 2011 7:42 am

Hi my friends!
I am trying to simulate the “NRELOffshrBsline_Monopile_RF” model that I downloaded from Jason Jonkman’s NRELOffshrBsline5MW public directory. To create a wind file I used the TurbSim turbulent wind simulator. I used the TurbSim.inp file that is provided when downloading TurbSim sw. I made some changes in that input file. These are the changes: NumGrid_Z = 31, NumGrid_Y = 31, AnalysisTime = 630, UsableTime = 630, HubHt = 90, GridHeight = 160, GridWidth = 200, refHt = 90, URef = 12 and CTEventFile = “C:\TSM_structures\EventData (Downloaded from NREL’s turbsim directory). The TimeStep is 0.05 and RandSeed1 = 2318573 and RandSeed2 = RANLUX. I renamed this input file “90m_12mps”. I executed TurbSim. It took almost one hour to create de .wnd .cts and .sum files. So I have copied these files into the Aerodata directory of FAST and I have executed FAST. The following error message has been shown: “An ADAMS control file for a LINEAR analysis can’t be built when using incident wave kinematics. Set WaveMod to 0 or MakeLINacf to False”. So I have set MakeLINacf to False in the “NRELOffshrBsline5MW_ADAMSSpecific” file. I have executed again FAST and the following error has been shown: GBRatio must be set to 1.0 when using Kink Pierce’s UserUSCont() routine. So I have set GBRatio to 1.0 in the “NRELOffshrBsline5MW_Monopile_RF” file. I have executed again FAST. This error appears: “Error: FF wind boundaries violated. Grid too small in Z direction (height (Z=-181.06m) is below the grid and no tower points are defined). Error getting velocity in Aerodyn/AD_WindVelocityWith disturbance(). And I am blocked because of this error; I don’t know how to solve it. Can anybody help me? Thanks in advance. Have a good day!

Jason.Jonkman
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Location: Boulder, CO
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Re: FAST

Postby Jason.Jonkman » Wed Apr 06, 2011 1:46 pm

Dear Jose Manuel Ezquerra,

I suspect your model is going numerically unstable. The error regarding FF wind boundaries is simply the first error that the program found.

The likely reason your model is going unstable is because you are not using the appropriate controller. The NREL 5-MW turbines do not use Kirk Pierce's sample variable-speed controller, UserVSCont_KP.f90, nor do they use Craig Hansen's sample pitch controller, PitchCntrl_ACH.f90. Instead, the NREL 5-MW turbine uses a torque and pitch controller implemented in GH Bladed-style DLL format. The DLL (i.e., DISCON.dll) is supplied with the NREL 5-MW models. These controllers require FAST’s interface to GH Bladed-style DLLs, which is not a default option in FAST v7.00.01. You can find a version of FAST with this interface here: http://wind.nrel.gov/public/jjonkman/FA ... erface.exe. Or if you’re adventurous, you can recompile FAST yourself using the guidance found in the FAST User’s Guide.

I hope that helps.

Bet regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

JoseManuel.Ezquerra
Posts: 4
Joined: Mon Apr 04, 2011 1:11 am
Organization: Ikerlan
Location: Spain

Re: FAST

Postby JoseManuel.Ezquerra » Thu Apr 07, 2011 12:48 am

Dear Jason!
Thank you very much for your fast answer! I did what you suggested me, this is, I dowloaded the Fast version of FAST, which is the one that interfaces to GH Bladed-style DLLs and it run perfectly. Thank you again! Have a nice daY!
Jose Manuel

Anuj.Gupta
Posts: 43
Joined: Thu Sep 27, 2012 6:53 am
Organization: Indian Institute of Technology Madras
Location: Chennai

Re: FAST

Postby Anuj.Gupta » Sun Jan 27, 2013 11:32 pm

Sir ,
As FAST don't have a theory manual i want to know on which scheme it works example CFD, FEM ,BEM .and wether it will take the effect of tower aerodynamics or not .

Jason.Jonkman
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Location: Boulder, CO
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Re: FAST

Postby Jason.Jonkman » Mon Jan 28, 2013 7:06 am

Dear Anuj Gupta,

For information on the FAST theory basis, see the forum topic found here, especially my post from December 15, 2010: viewtopic.php?f=4&t=424. To answer your direct questions:

*FAST is based on combined modal and multi-body dynamics formulation with nonlinear beam elements.
*FAST's aerodynamics module (AeroDyn) is based on a blade-element/momentum (BEM) or generalized dynamic wake (BEM) wake model, together with a Beddoes-Leishman dynamic stall model.
*The direct wind load on the tower is not currently included, but it is something we are working to add.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Anuj.Gupta
Posts: 43
Joined: Thu Sep 27, 2012 6:53 am
Organization: Indian Institute of Technology Madras
Location: Chennai

Re: FAST

Postby Anuj.Gupta » Fri Feb 01, 2013 10:08 pm

Dear Janson,
Thanks for the reply . i want to know that how can we get the mode shapes plot .I am attaching a fig of tower mode shape .
Attachments
Capture.PNG
mode shape fig.
Capture.PNG (41.32 KiB) Viewed 21122 times

Jason.Jonkman
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Location: Boulder, CO
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Re: FAST

Postby Jason.Jonkman » Tue Feb 05, 2013 1:26 pm

Dear Anuj,

If you already know the coefficients c_i for i = 2, 3, ... 6 for the mode shapes you want to plot, the mode shape can be plotted as y versus x of the following polynomial:

y(x) = SUM( c_i*x^i, i = 2, 3, ...6) for x <= 0 <= 1

Please note:
y(0) = 0 (the mode shape is always for a cantivered beam)
y(1) = 1 = SUM( c_i, i = 2, 3, ...6) (the mode shape is normalized by the tip displacement)

I hope that helps.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Anuj.Gupta
Posts: 43
Joined: Thu Sep 27, 2012 6:53 am
Organization: Indian Institute of Technology Madras
Location: Chennai

Re: FAST

Postby Anuj.Gupta » Tue Feb 05, 2013 8:53 pm

Sir,
I want to know that FAST will give these mode shapes in output or we are giving as a input to FAST , as i see in Baselinetower.dat and Baselineblade.dat ,there is something written at the last about mode shapes and coefficient.

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: FAST

Postby Jason.Jonkman » Wed Feb 06, 2013 12:22 am

Dear Anuj,

The blade and tower mode shapes are input to FAST (as specified by the polynomial coefficients in the FAST blade and tower input files). These can be derived from BModes: http://wind.nrel.gov/designcodes/preprocessors/bmodes/. More information can be found from: viewtopic.php?f=4&t=173.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Anuj.Gupta
Posts: 43
Joined: Thu Sep 27, 2012 6:53 am
Organization: Indian Institute of Technology Madras
Location: Chennai

Re: FAST

Postby Anuj.Gupta » Sun Feb 10, 2013 11:38 pm

Dear Jonkman,
I have a question that suppose we are running a simulation for 500 sec and we want to change some data in between simulation then how can we do that, suppose we have to change the blade mass properties at 100 sec .then how can we do that?

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: FAST

Postby Jason.Jonkman » Mon Feb 11, 2013 2:17 pm

Dear Anuj,

It is not possible in FAST to change the blade mass in the middle of a simulation. I'm not sure why one would want to anyway.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Anuj.Gupta
Posts: 43
Joined: Thu Sep 27, 2012 6:53 am
Organization: Indian Institute of Technology Madras
Location: Chennai

Re: FAST

Postby Anuj.Gupta » Mon Feb 11, 2013 10:03 pm

I am asking this because i read one paper of Kim and Yae in that paper they are doing the analysis for a partially broken blades and they are doing like that i.e after 100 sec of simulation they are changing the blade properties .

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: FAST

Postby Jason.Jonkman » Tue Feb 12, 2013 6:20 am

Dear Anuj,

Kim and Bae have also made their own customizations to FAST. It is not possible in the standard version of FAST to change the blade mass in the middle of a simulation.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Neeraj.Kumar
Posts: 6
Joined: Thu Jul 25, 2013 12:30 am
Organization: IIT madras
Location: india

Re: FAST

Postby Neeraj.Kumar » Mon Jul 29, 2013 3:40 am

Dear sir,
I am trying to simulate the “NRELOffshrBsline5MW_OC3_Hywind” model that I downloaded from Jason Jonkman’s NRELOffshrBsline5MW public directory.First of all the wind file is not given in the directory for 5MW so I have taken 1.5MW wind file and did appropriate changes such that hub height =90m, wind speed =11 m/s,AnalysisTime =600, GridHeight=155 , GridWidth=155 and then i have simulate windfile in cmd prompt as "turbsim windfile.inp".Then it is terminating normally and generating wnd file which is further used in AERODYN while simulating the FAST fst file.

but when i start simulating the fst file it is giving error as:
small angle assumption violated in SUBROUTINE smllRotTrans<> due to large blade deflection

Blade element #1 is supersonic

Grid in y direction is small

error getting velocity in aerodyn

I have made changes in grid width and grid height several times but it is not terminating. Please guide me if am doing anything wrong or there is another way to complie this 5MW Files instead of compiling in cmd prompt.How we can remove this "grid error and error getting velocity in aerodyn".

kindly suggest me

with regards
Neeraj.Kumar

Jason.Jonkman
Posts: 4622
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: FAST

Postby Jason.Jonkman » Mon Jul 29, 2013 6:56 am

Dear Neeraj,

We purposely left out the wind files from the NREL 5-MW model archives because adequately sized wind files for the NREL 5-MW are typically very large. See the last four posts on the forum topic linked here for an explanation and for a link to where you can download a TurbSim input file for this turbine: viewtopic.php?f=4&t=341.

Warnings regarding a “small angle approximation violation,” warnings regarding “supersonic blades,” a simulation crash, or very large deflections that occur in the time series near the start of a simulation are good signs of a numerical instability. Without knowing more about your simulation settings, it's hard to know that what the problem is. But the NREL 5-MW turbine models should not have these problems, unless you've customized the model in some unphysical way. See the following forum topic for more information: viewtopic.php?f=4&t=272.

I don't understand your question about compiling. Input files don't need compiling and you don't need to recompile FAST unless you need to make changes to the source code.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov


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