Search found 56 matches

by Lorenzo.Cottura
Tue Dec 08, 2020 7:27 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason,
Using the matrix in equation (2) in your 2009 paper instead of the Euler matrix my results correspond to the FAST outputs. I didn't think this replacement could affect that much. Thank you so much for the help you have given me.
Best regards,
Lorenzo.
by Lorenzo.Cottura
Fri Dec 04, 2020 10:42 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason, I think I have found the problem, which is the mass matrix. To obtain the accelerations according to the inertial coordinate system, having the loads oriented in this reference system, the mass matrix must also be referred to the inertial reference system. Starting from the mass matrix i...
by Lorenzo.Cottura
Mon Nov 30, 2020 5:24 pm
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason, Yes, in this case (that is an onshore test) my tower base loads are the same of the outputs TwrBsFx, TwrBsFy, TwrBsFz, TwrBsMx, TwrBsMy, TwrBsMz in the OutData. My model has the same outputs of FAST both when I do not consider the aerodynamic loads (considering only hydrodynamics, I find...
by Lorenzo.Cottura
Mon Nov 30, 2020 4:52 pm
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason,
Yes, I’m referring to GenTq, sorry for the incorrect reference.
Despite this, the error on Mx persists, as mentioned in the previous post.
Best regards,
Lorenzo
by Lorenzo.Cottura
Mon Nov 30, 2020 8:50 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason, You are right: without aerodynamics loads everything matches. As you observed, by carrying out an onshore test I noticed that using the Control Torque I obtained a right Mx_tow=TwrBsMx (output in OutData), while with RotAeroMx the outputs did not return. So, I also tried using Mx_nac=Cnt...
by Lorenzo.Cottura
Sat Nov 28, 2020 9:27 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason, I thank you for the great help you are giving me. When you talk about our topic linked above, you are referring to the image below, which however refers to a test with CompAero = 0, so we are talking about a test in the absence of aerodynamic loads. In this case, I agree, the error is ca...
by Lorenzo.Cottura
Fri Nov 27, 2020 9:24 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason My question is if all the loads reported by me in the previous post are in the same coordinate system parallel to the inertial frame coordinate system, and if multiplying these by inv(M) I can get the accelerations ['PtfmTAxi' 'PtfmTAyi' 'PtfmTAzi' 'PtfmRAxi' 'PtfmRAyi' 'PtfmRAzi']). Best...
by Lorenzo.Cottura
Fri Nov 27, 2020 8:25 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Re: Switching from 'RtAero' to TwrBs in an offshore test

Dear Jason, As for TransMat, I have previously verified that my TransMat matrix gives the same results as the matrix in Eq. 2 of the article you mentioned. And I presume you want (0,0,0) to translate with the platform transnational DOFs rather than be fixed to the inertial frame? As for your final t...
by Lorenzo.Cottura
Thu Nov 26, 2020 9:17 am
Forum: Structural Analysis
Topic: Switching from 'RtAero' to TwrBs in an offshore test
Replies: 17
Views: 2416

Switching from 'RtAero' to TwrBs in an offshore test

I noticed that in the FAST OutData, for an offshore test, 'TwrBsFxt', 'TwrBsFyt', 'TwrBsFxt', 'TwrBsMxt', 'TwrBsMyt', 'TwrBsMzt' also contain inertial loads, and that moreover they are integral with the tower and not with the inertial reference system. My goal is to have the loads at the base of the...
by Lorenzo.Cottura
Fri Nov 20, 2020 11:48 am
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason, Your values are slightly different than what is found in the ElastoDyn summary, which is likely the main reason for the small difference between our numbers. What values are you referring to? I took Ihub = 115926; Rhub = 1.5; Igen = 534.116; directly from the ElastoDyn summary, while Mbl...
by Lorenzo.Cottura
Fri Nov 20, 2020 8:48 am
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason, If GenTq*GBRatio does not exactly equal RtAeroMxh, then the rotor will accelerate (or decelerate). If you are setting GenTq directly from an output of RtAeroMxh, numerical round off could play a role if you RtAeroMxh is truncated in the output file (true for ASCI output, but full precisi...
by Lorenzo.Cottura
Thu Nov 19, 2020 9:22 am
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason, Here the ServoDyn file used: ------- SERVODYN v1.05.* INPUT FILE -------------------------------------------- NREL 5.0 MW Baseline Wind Turbine for Use in Offshore Analysis. Properties from Dutch Offshore Wind Energy Converter (DOWEC) 6MW Pre-Design (10046_009.pdf) and REpower 5M 5MW (5m...
by Lorenzo.Cottura
Thu Nov 19, 2020 8:54 am
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason,
I'm using 'RtAeroMxh' and 'GenTq' from FAST OutData.
Best regards,
Lorenzo.
by Lorenzo.Cottura
Thu Nov 19, 2020 5:12 am
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason, Thanks for your reply. I still have a little doubt: in a steady test, in order to have constant rotor speed, according to the formula reported above, after the initial transient it should be RtAeroMxh = GenTq*Ngear. Schermata 2020-11-19 alle 13.01.39.png Instead, as you can see from the ...
by Lorenzo.Cottura
Wed Nov 18, 2020 12:05 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine
Replies: 28
Views: 2679

Re: Difference between 'RtAeroMxh' and 'RotTorq' in an onshore turbine

Dear Jason,
In my simulation I setted Precone=0.
Do I still have to take this into account when calculating Irot?
Best regards,
Lorenzo.

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