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by Jason.Jonkman
Tue Apr 13, 2021 6:52 am
Forum: Controls
Topic: Information on couplings needed
Replies: 1
Views: 12

Re: Information on couplings needed

Dear Bartosz, The aerodynamic loads on the rotor will include a torque, which will tend to induce roll/sway of the floater. There will also be gyroscopic loads from the spinning rotor, which mainly induce yaw, but when the rotor is tilted (due to shaft tilt or floater heal), could also induce roll. ...
by Jason.Jonkman
Mon Apr 12, 2021 9:54 am
Forum: Controls
Topic: A question concerning Cp surface generation with OpenFAST
Replies: 3
Views: 25

Re: A question concerning Cp surface generation with OpenFAST

Dear Bartosz, Yes, if you have DOFs enabled (structural or aerodynamic) , it would likely make sense to allow the dynamics to settle until a steady state is reached before switching to the next pitch angle. If you've disabled the generator DOF in ElastoDyn (GenDOF = False), then there is no need to ...
by Jason.Jonkman
Mon Apr 12, 2021 9:13 am
Forum: Controls
Topic: A question concerning Cp surface generation with OpenFAST
Replies: 3
Views: 25

Re: A question concerning Cp surface generation with OpenFAST

Dear Bartosz, If you have eliminated all dynamics (degrees of freedom)--both structural and aerodynamic--then you should be able to generate the aerodynamic surface as you have. It sounds like you've already eliminated all structural DOFs in ElastoDyn. Aerodynamically, the equivalent would be quasi-...
by Jason.Jonkman
Mon Apr 12, 2021 8:56 am
Forum: Computer-Aided Engineering Software Tools
Topic: Confusion about IceDyn
Replies: 5
Views: 132

Re: Confusion about IceDyn

Dear Tianhui, The warnings you are getting sound similar to the ones you are reporting in the related forum post-- https://wind.nrel.gov/forum/wind/viewtopic.php?f=4&t=2679. However, if set the wind speed to practically zero, you should also disable wake and unsteady airfoil aerodynamic calculat...
by Jason.Jonkman
Mon Apr 12, 2021 8:43 am
Forum: Computer-Aided Engineering Software Tools
Topic: Question about Turbsim
Replies: 3
Views: 52

Re: Question about Turbsim

Dear Tianhui.Liu, I don't see any errors--in fact the simulation terminated normally--but there are still many warnings about large angle of attack, which again suggests to me that your controller is not functioning properly or your initial conditions are not set as properly. The expected (mean) val...
by Jason.Jonkman
Mon Apr 12, 2021 8:33 am
Forum: Computer-Aided Engineering Software Tools
Topic: Fast errors for extreme load cases
Replies: 5
Views: 52

Re: Fast errors for extreme load cases

Dear Patrick,

You've already disabled the wake calculation, but to eliminate this error, it may help to also set InfModel = EQUIL.

Best regards,
by Jason.Jonkman
Fri Apr 09, 2021 9:17 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Fast errors for extreme load cases
Replies: 5
Views: 52

Re: Fast errors for extreme load cases

Dear Patrick, To disable the wake and unsteady airfoil aerodynamic calculations in AeroDyn v12.58, set StallMod = STEADY and IndModel = NONE. Not using these settings may be the cause of the instability you are seeing. Which soil-structure interaction model are you using in FAST v7? You may be inter...
by Jason.Jonkman
Fri Apr 09, 2021 8:33 am
Forum: Computer-Aided Engineering Software Tools
Topic: Fast errors for extreme load cases
Replies: 5
Views: 52

Re: Fast errors for extreme load cases

Dear Patrick, Well, it looks like your model has gone numerically unstable, but I'm not sure why. You haven't shared your AeroDyn input file, but have you disabled the wake calculation and unsteady airfoil aerodynamic calculation as recommend for an idling condition? Please note that the case you ar...
by Jason.Jonkman
Thu Apr 08, 2021 10:56 am
Forum: Computer-Aided Engineering Software Tools
Topic: Simulation with hydrodynamic loads only
Replies: 5
Views: 143

Re: Simulation with hydrodynamic loads only

Dear Malte, For this parked case, have you disabled the wake model in AeroDyn (WakeMod = 0), which is only valid for operational conditions? Are the blades pitched/feathered to 90-degrees or flat into the wind (0 degrees)? Are you neglecting the simulation start-up transient before extracting the ma...
by Jason.Jonkman
Thu Apr 08, 2021 7:29 am
Forum: Computer-Aided Engineering Software Tools
Topic: Confusion about IceDyn
Replies: 5
Views: 132

Re: Confusion about IceDyn

Dear Tianhui.Liu,

I'm not actually aware of any changes to IceDyn made within OpenFAST. In fact, the sample IceDyn input file still refers to v1.01--see: https://github.com/OpenFAST/r-test/blob ... _Input.dat.

Best regards,
by Jason.Jonkman
Thu Apr 08, 2021 7:14 am
Forum: Structural Analysis
Topic: Fixed offshore wind turbines Properties Question
Replies: 3
Views: 107

Re: Fixed offshore wind turbines Properties Question

Dear Tianhui, Are you asking for the full-system natural frequencies for each of these fixed-bottom offshore wind systems in the parked/idling condition? These are available in the following publications: OC3-monopile: Figure 6 of NREL/TP-5000-48191: https://www.nrel.gov/docs/fy11osti/48191.pdf OC3-...
by Jason.Jonkman
Thu Apr 08, 2021 6:53 am
Forum: General
Topic: FAST.Farm
Replies: 176
Views: 21443

Re: FAST.Farm

Dear Younes, You are plotting the low-resolution domain, but the problem is with the high-resolution domain. From your input file specification, the high-resolution domain extends from 50 to 140 m in the global FAST.Farm coordinate system, which is -76 to 14 m in the local wind turbine coordinate sy...
by Jason.Jonkman
Wed Apr 07, 2021 11:06 am
Forum: General
Topic: FAST.Farm
Replies: 176
Views: 21443

Re: FAST.Farm

Dear Younes,

The error is not obvious to me from my quick skim (and I'm not following all of your control logic, particularly "ind", but haven't spent much time to understand). I suggest compiling in debug mode and stepping through the solution with the debugger.

Best regards,
by Jason.Jonkman
Wed Apr 07, 2021 6:26 am
Forum: General
Topic: FAST.Farm
Replies: 176
Views: 21443

Re: FAST.Farm

Dear Younes, The error means that the DISCON_SC.dll is accessing memory it shouldn't be. In the supercontroller interface, from_SC() is an array of size NumSC2Ctrl*nTurbines and to_SC() is allocated to a array of size NumCtrl2SC*nTurbines, but the DISCON_SC.dll of each wind turbine can only access v...
by Jason.Jonkman
Tue Apr 06, 2021 3:38 pm
Forum: Computer-Aided Engineering Software Tools
Topic: hydrodynamic analysis of multi body platform
Replies: 18
Views: 2850

Re: hydrodynamic analysis of multi body platform

Dear Josh, Regarding the damping plots, I see the damping converging to 0 at low frequency. Most curves also converge to zero at high frequency, but this is not the case for B(6,6) (yaw-yaw), at least by 4 rad/s. I'm also a bit surprised by the lack of smoothness in the data and very distinct peaks,...

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