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by Jason.Jonkman
Mon Jun 01, 2020 6:42 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

To debug this, I need to have the input files associated with Solution 1 and Solution 2 to see what is different between the two solutions. Please attach those.

Best regards,
by Jason.Jonkman
Sat May 30, 2020 8:12 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak, To answer your question, I need to understand what the difference is between these two FAST solutions: Solution 1 At first I find the optimal value for the TSR and Cp of the turbine. Solution 2 Next I do the calculations in opposite direction: If I set that turbine to rotate at fixed opt...
by Jason.Jonkman
Sat May 30, 2020 8:09 am
Forum: Testing
Topic: OpenFast Regression tests
Replies: 15
Views: 12157

Re: OpenFast Regression tests

Dear Francesco, If the plots look reasonable to you, I'm sure the solution is fine and you are can proceed running OpenFAST for your analysis. The OpenFAST r-test is highly sensitive and will indicate failures due to differences in compiler, platform, precision, source code changes, etc., even thoug...
by Jason.Jonkman
Fri May 29, 2020 5:58 pm
Forum: Computer-Aided Engineering Software Tools
Topic: simulate pitch offset with FAST
Replies: 6
Views: 1593

Re: simulate pitch offset with FAST

Dear Bruno, From my brief skim of your input files, I don't see any obvious problems other than the poor initial conditions. Instead of setting all initial conditions to zero, it is generally recommend to set the initial rotor speed and initial blade-pitch angles in ElastoDyn to be their expected va...
by Jason.Jonkman
Fri May 29, 2020 5:41 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

We seem to be going in circles and I'm not sure how to help. Do you have two distinct FAST models, where one predicts the answer you expect and the other does not? If so, what is different between these models?

Best regards,
by Jason.Jonkman
Fri May 29, 2020 3:23 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

So, at what condition can you run FAST and get Cpmax = 0.42 and how does that condition differ from the simulation at 10 m/s and TSR = 5.6?

Best regards,
by Jason.Jonkman
Fri May 29, 2020 2:59 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak, For every wind speed, if I calculate the rotor speed according to the optimal value of the TSR and setting the pitch angle to its optimal value, I expect that the Cp to be its maximum value, right? So it does not depend on special wind speed. In other words, by for every wind speed by se...
by Jason.Jonkman
Fri May 29, 2020 12:48 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

OK, so you say at 10 m/s and rotor speed = (5.6*10)/2.9 you get lower Cpmax than you expect. At what wind speed and corresponding rotor speed are you getting the Cpmax that you do expect?

Best regards,
by Jason.Jonkman
Fri May 29, 2020 12:19 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

Are these files the ones that give you the answer that you expect (correct Cp)? What do you change in these files to get the answer that you don't expect (low Cp)?

Best regards,
by Jason.Jonkman
Fri May 29, 2020 11:11 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

So, can you share two sets of FAST input files that you expect to produce the same result, but don't?

Best regards,
by Jason.Jonkman
Fri May 29, 2020 9:16 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

I'm not understanding. Are you saying that for the same TSR and pitch, FAST is giving you different results for different wind speeds (equating to different rotor speeds because TSR is the same), even with all structural DOFs disabled?

Best regards
by Jason.Jonkman
Fri May 29, 2020 8:37 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak,

I'm not an expert on this SWRT model. I would try repeating this analysis at different TSR and pitch angle values to obtain the Cp surface.

Best regards,
by Jason.Jonkman
Fri May 29, 2020 6:46 am
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 108
Views: 11717

Re: Linearization issue using Fast V7.02

Dear Babak, I would not expect this characteristic of most Cq and Cp versus TSR curves to be the cause of the issue you are seeing. I think the FAST model simply predicts a lower power than you are expecting. I would verify this through time-domain simulations, independent from a linearization analy...
by Jason.Jonkman
Thu May 28, 2020 7:11 am
Forum: Computer-Aided Engineering Software Tools
Topic: Blade nodes in BeamDy and ElastoDyn
Replies: 6
Views: 948

Re: Blade nodes in BeamDy and ElastoDyn

Dear Kemal,

Yes, your input looks correct. The value of RNodes in the ElastoDyn summary is the distance along the pitch axis from the hub center to each blade analysis node, and you've identified the correct nodes in the BldGagNd list.

Best regards,
by Jason.Jonkman
Thu May 28, 2020 7:06 am
Forum: Computer-Aided Engineering Software Tools
Topic: simulate pitch offset with FAST
Replies: 6
Views: 1593

Re: simulate pitch offset with FAST

Dear Bruno, Yes, adding a constant offset to BlTwist will result in an aerodynamic pitch imbalance (this feature was not available when I responded to Felix in Dec, 2010). What is the difference between B1/-2, B2-2, and B3-2 (likewise for +)? Are you simply toggling which blade has the twist offset ...

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