Search found 5771 matches

by Jason.Jonkman
Tue May 18, 2021 8:50 am
Forum: Computer-Aided Engineering Software Tools
Topic: Invalid numeric input
Replies: 1
Views: 5

Re: Invalid numeric input

Dear Kevin, I'm not familiar with this error and can't find a reference to "StiffXX" in the FAST v7.02 source code. Where did you get the version of FAST v7.02 that you are running? Do you have the same problem if running the FAST v7.02 found from my Google drive: https://drive.google.com/...
by Jason.Jonkman
Mon May 17, 2021 4:50 pm
Forum: Inflow Turbulence
Topic: Turbsim spatial averaging
Replies: 1
Views: 10

Re: Turbsim spatial averaging

Dear Deepali, When you calculate the turbulence at the hub, are you referring to an output from the InflowWind module of OpenFAST? The InflowWind module will perform 3D interpolation (2 spatial + time) when calculating the wind inflow at points (user-specified points or aerodynamic analysis nodes) t...
by Jason.Jonkman
Mon May 17, 2021 4:39 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Heydrodynamic coefficients HELP!
Replies: 14
Views: 73

Re: Heydrodynamic coefficients HELP!

Dear Bartosz, It looks like you are only seeing one mode because VTKLinModes = 1 in your mode-shape visualization file. Yes, you need to have loads acting on the platform as inputs to derive the 6x6 rigid-body mass matrix. These are available by setting LinInputs = 2 in the OpenFAST primary (*.fst) ...
by Jason.Jonkman
Mon May 17, 2021 3:38 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Heydrodynamic coefficients HELP!
Replies: 14
Views: 73

Re: Heydrodynamic coefficients HELP!

Dear Bartosz, It looks like there are many warnings about large angles, but it also said OpenFAST terminated normally. So, what do you mean that "other modes are not generated"? What does your ED_HWS_CASE_0_MODSHPSMBC.viz file look like? You can probably eliminate the warnings by reducing ...
by Jason.Jonkman
Mon May 17, 2021 2:01 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Heydrodynamic coefficients HELP!
Replies: 14
Views: 73

Re: Heydrodynamic coefficients HELP!

Dear Bartosz, Yes, your linearization process sounds correct. The OpenFAST linearizations do not show the mass matrix directly, but this matrix can often be inferred from other matrices generated through the linearization process. A similar question was asked and answered in the following forum topi...
by Jason.Jonkman
Mon May 17, 2021 1:54 pm
Forum: General
Topic: Platform Additional Stiffness and Damping
Replies: 10
Views: 3466

Re: Platform Additional Stiffness and Damping

Dear Brendan, Good question. The improvements to HydroDyn related to floating platform structural flexibility and member-level loads mentioned in the above-referenced issue (https://github.com/OpenFAST/openfast/issues/245) have now been completed and released in OpenFAST v2.6. Included in that effor...
by Jason.Jonkman
Mon May 17, 2021 10:10 am
Forum: Structural Analysis
Topic: OC3-Hywind eigenanalysis
Replies: 1
Views: 19

Re: OC3-Hywind eigenanalysis

Dear Hao Nguyen, I would think you'd need to include the off-diagonal coupling terms to predict the correct natural frequencies of the NREL 5-MW turbine atop the OC3-Hywind spar buoy. The full-system mass, center of mass, and inertia of the OC3-Hywind system, from which the 6x6 mass matrix can be fo...
by Jason.Jonkman
Mon May 17, 2021 8:20 am
Forum: Structural Analysis
Topic: Processing OpenFast linearization output
Replies: 58
Views: 9224

Re: Processing OpenFast linearization output

Dear Younes,

I would guess there is some excitation happening at the period of the response, which I estimate at about 3.6 s or 0.278 Hz, e.g., wave excitation or a harmonic of the rotor speed. What incident waves (WaveTp) have you defined? What is the rotor speed you are simulating?

Best regards,
by Jason.Jonkman
Mon May 17, 2021 8:05 am
Forum: Airfoils
Topic: Inlet Velocity for DU 35 and DU 40 Airfoils
Replies: 7
Views: 96

Re: Inlet Velocity for DU 35 and DU 40 Airfoils

Dear Victor, Yes, those are the correct airfoil coordinates. These coordinate files are also available along with the airfoil data in the FAST v8 archive and OpenFAST r-test. I'm not sure what differences you are seeing, but please be aware that the airfoil data NREL has provided includes 3D correct...
by Jason.Jonkman
Fri May 14, 2021 4:08 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Heydrodynamic coefficients HELP!
Replies: 14
Views: 73

Re: Heydrodynamic coefficients HELP!

Dear Bartosz, OK, thanks for clarifying. The natural frequencies of the platform modes will be dictated by the full system mass / inertia (including added mass) and stiffness (including hydrostatic and mooring), and will thus be based on the system configuration (geometry, material properties). If t...
by Jason.Jonkman
Fri May 14, 2021 11:47 am
Forum: Computer-Aided Engineering Software Tools
Topic: Heydrodynamic coefficients HELP!
Replies: 14
Views: 73

Re: Heydrodynamic coefficients HELP!

Dear Bartosz, I'm not sure I understand the problem you are describing. What are the various results you are plotting (I don't understand the labels: ORE Catapult and OpenFAST, N-S, E-W, etc.)? What is the difference between HWS.png and SurgeSawySparInput.png ? I see some basic differences in your f...
by Jason.Jonkman
Fri May 14, 2021 9:20 am
Forum: Structural Analysis
Topic: Retrieve information about wind turbine model
Replies: 4
Views: 121

Re: Retrieve information about wind turbine model

Dear Junius, Most of the models in the OpenFAST r-test came from the original CertTest in FAST v8, which are documented in Table 6 of the FAST v8 ReadMe file: https://drive.google.com/file/d/17LDwMnCVmLfbRWSaVFxxqphVrtawMwlj/view?usp=sharing. What type of wind turbine model do you want to use? Best ...
by Jason.Jonkman
Fri May 14, 2021 6:56 am
Forum: Computer-Aided Engineering Software Tools
Topic: FF wind array boundaries violated
Replies: 3
Views: 30

Re: FF wind array boundaries violated

Hi Atinuke, I'm not sure I know what is the underlying problem based on the information provided, but just a few comments: ⋅ The Y-direction error is much more sensible in that the aerodynamic analysis node lies just outside the wind domain, such that increasing the width of the domain may...
by Jason.Jonkman
Thu May 13, 2021 5:25 pm
Forum: Computer-Aided Engineering Software Tools
Topic: FF wind array boundaries violated
Replies: 3
Views: 30

Re: FF wind array boundaries violated

Dear Atinuke, The error is being triggered because the position of an aerodynamic analysis node is NaN (Not a Number). This suggests that your model has gone numerically unstable, resulting in unrealistically large motions. It looks like the simulation failed about 50 s in; I would guess you are see...
by Jason.Jonkman
Thu May 13, 2021 3:55 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3092

Re: The frequency component of flapwise

Dear Feng, The hydrostatic stiffness matrix (CH in your example) includes the effects of waterplane area and center of buoyancy, but it does not include the effects of full system body mass and center of mass. The full system mass matrix linked in the forum topic linked above (M in your example) inc...

Go to advanced search