Search found 4483 matches

by Jason.Jonkman
Sat Jan 18, 2020 1:41 am
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina, The error regarding "no valid value of phi" has been discussed many times on this forum was fixed in versions of AeroDyn v15 newer than FAST v8.16. I suggest that you upgrade from FAST v8.16 to OpenFAST: https://github.com/OpenFAST/openfast. Regarding the large oscillations in r...
by Jason.Jonkman
Sat Jan 18, 2020 1:34 am
Forum: Computer-Aided Engineering Software Tools
Topic: FASTV8-HydroDyn-Wavemode5
Replies: 5
Views: 419

Re: FASTV8-HydroDyn-Wavemode5

Dear Zhou.Lin, The WaveMod=5 option of HydroDyn uses the user-specified wave-elevation time history to calculate the wave kinematics throughout the fluid domain. Any of the hydrodynamic load models of HydroDyn (strip theory or potential flow) can be enabled. Presumably you've enabled strip theory (M...
by Jason.Jonkman
Fri Jan 17, 2020 9:23 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Initial pitch with bladed-style dll
Replies: 4
Views: 104

Re: Initial pitch with bladed-style dll

Dear Kemal,

Looking at the Bladed-DLL interface in FAST / OpenFAST (BladedInterface.f90), it appears that the interface only supports pitch-angle actuation (avrSWAP(10)=0). I would suggest changing your controller to use pitch-angle actuation or change the BladedInterface.f90.

Best regards,
by Jason.Jonkman
Fri Jan 17, 2020 9:15 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Linearization issue using Fast V7.02
Replies: 54
Views: 8341

Re: Linearization issue using Fast V7.02

Dear Emily,

It is easy to specify zero initial conditions through the FAST v7 input file (set all initial conditions, including RotSPeed, to zero). Do you get the behavior you want then? What initial conditions did you have when you had the issue?

Best regards,
by Jason.Jonkman
Fri Jan 17, 2020 9:11 pm
Forum: Rotor Aerodynamics
Topic: Emergency shutdown
Replies: 4
Views: 65

Re: Emergency shutdown

Dear Moritz,

Well, I'm not sure. I would guess the strong oscillation in rotor speed and blade-root moment are related. Do you get the same behavior with simplified aerodynamics, i.e., WakeMod = 1, AFAeroMod = 1?

Best regards,
by Jason.Jonkman
Thu Jan 16, 2020 9:07 am
Forum: Wind Farm Modeling
Topic: Error in running TurbSim
Replies: 4
Views: 1502

Re: Error in running TurbSim

Dear Vahid,

A similar question was asked and answered in my post dated May 19, 2015 in the following forum topic: viewtopic.php?f=4&t=268&p=5676.

Best regards,
by Jason.Jonkman
Thu Jan 16, 2020 12:55 am
Forum: Computer-Aided Engineering Software Tools
Topic: Initial pitch with bladed-style dll
Replies: 4
Views: 104

Re: Initial pitch with bladed-style dll

Dear Kemal,

Well, I would guess the problem is in your DLL. Setting the initial (nonzero) pitch angle in ElastoDyn is correct, but it sounds like your controller is overriding this and stepping it to zero degrees.

Best regards,
by Jason.Jonkman
Tue Jan 14, 2020 1:58 pm
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina, Yes, you've disabled the structural DOFs and eliminated shaft tilt, so, the aerodynamic loads differ, and the blade-pitch angles appropriate to each mean wind speed will change. You'll have to calculate the blade-pitch angle at each wind speed necessary to obtain the desired rotor speed, ...
by Jason.Jonkman
Tue Jan 14, 2020 1:04 pm
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina,

I gather based on your description that the aerodynamic torque and generator torque are not balanced for the given wind speed, blade-pitch angle, and generator torque, so, the rotor speed will accelerate/decelerate until they are balanced.

Best regards,
by Jason.Jonkman
Tue Jan 14, 2020 8:50 am
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina,

It sounds like you've enabled the generator DOF, but haven't activated any generator torque within ServoDyn, thus, the rotor is accelerating until the aerodynamic power drops to zero.

Best regards,
by Jason.Jonkman
Tue Jan 14, 2020 7:55 am
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina, When you disable the generator DOF, the generator will rotate at a fixed speed (the initial speed) regardless of the torques applied. If you want time-varying generator speed, you must enable the generator DOF in ElastoDyn (GenDOF = True). The error you are getting is not related to the l...
by Jason.Jonkman
Mon Jan 13, 2020 1:46 pm
Forum: Computer-Aided Engineering Software Tools
Topic: clarification of force along axis
Replies: 1
Views: 53

Re: clarification of force along axis

Hi Arnold,

That is not the case in the ElastoDyn module. To apply the loads transferred to the hub from a blade, both the forces and moments at the root should be used.

Best regards,
by Jason.Jonkman
Mon Jan 13, 2020 1:40 pm
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina,

I see that you've enabled tower potential flow (TwrPotent=1). You should get constant results after disabling this feature (TwrPotent=0).

Best regards,
by Jason.Jonkman
Mon Jan 13, 2020 10:34 am
Forum: Controls
Topic: Model verification
Replies: 42
Views: 687

Re: Model verification

Dear Sina,

You've disabled all structural DOFs and eliminated shaft tilt, yaw, wind direction, and wind shear. Do you have tower influence or tower shadow enabled in AeroDyn v15? These could also induce skewed flow.

Best regards,
by Jason.Jonkman
Mon Jan 13, 2020 10:25 am
Forum: Computer-Aided Engineering Software Tools
Topic: Modelling of a single point mooring system
Replies: 4
Views: 120

Re: Modelling of a single point mooring system

Dear Shuijin, You can choose to enter a stiffness matrix in FAST / OpenFAST rather than to enable a mooring module. The 6x6 stiffness matrix can be specified as AddClin in HydroDyn. Presumably you also have a 6x1 vector of preloads, which you can enter as AddF0 in HydroDyn. I'm not aware of any capa...

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