openfast v2.3

Wind & Water General
1

Dear all,

My name is Gonzalo Ahedo, an Spanish engineer working in the offshore sector. Some months ago, I started simulating with DTU10MW WTG, and for that, I have been using FAST v8 without any problems.

But recently, analysing the trends of the offshore wind market, I have decided to use the new model of NREL15MW. For that model (github.com/OpenFAST/openfast/releases).
After downloading all the necessary archive and preparing my simulations data, I encountered with the following error:

“It is not found the entry point of the procedure for_reallhoc_lhs in the library of dinamyc links (and the direction of the .exe)”

Unfortunately I do not understand to what is refering with this message, and I am not able to find anything useful in the Internet. So, I come here to ask if someone has face with the same problem and/or knows how to solve it.

Thanks in advanced,

Gonzalo

2

Hey all
Does OpenFAST consider the coupled dynamics of the platform structure and tower in the case of floating offshore wind turbine?

Thanks in advance
Akheel

3

Dear Gonzalo – Sorry, but I’m not familiar with this error. I would suggest posting your question on GitHub issues (either in OpenFAST or for the NREL 15-MW turbine).

Dear Akheel – Yes, OpenFAST considers the coupled dynamics of the platform and tower for floating offshore wind turbines. That said, in OpenFAST v2.3, the platform is considered a six degrees of freedom rigid body. We are working on an upgrade to OpenFAST to support the structural flexibility and member-level loads of the floating platform, which will be available in a future OpenFAST release.

Best regards,

4

Hi all,

I am working with a floating wind turbine model which was build in FASTv8.16. Now, I want to modify the files in order to run the simulation with openFAST (v2.3.0). Although I have worked with transitions of previous versions of FAST to newer ones (v15 to v16 for example), I cannot figure out how it works for openFAST. I have checked the deleted and added lines in openFAST documentation so I suppose that regarding the .fst file I have to do it manually. Concerning the HydroDyn I have checked that there is a matlab tool for this purpose. Nevertheless, the simulation does not run smoothly as it was with FASTv8.16. One extra thing that confuses me is the module AeroDyn Airfoil Input File -Airfoil Tables (Added in OpenFAST v2.3.0 according to documentation). Is it something additional since I cannot find a similar module on previous FAST versions?

Thank you in advance.

Best regards,
Ioannis.

Edit: this is the error
Processed 108800 time steps of 20-Hz full-field data (5440 seconds).
Running ServoDyn.
Running ServoDyn Interface for Bladed Controllers.
Running HydroDyn.
Generating incident wave kinematics and current time history.

FAST_InitializeAll:HydroDyn_Init:Waves_Init:VariousWaves_Init:Cannot allocate array WaveAcc0Hxi.
VariousWaves_Init:Cannot allocate array WaveAcc0Hyi.
VariousWaves_Init:Cannot allocate array WaveAcc0V.
VariousWaves_Init:Cannot allocate array InitOut%WaveDynP.
VariousWaves_Init:Cannot allocate array InitOut%WaveVel.
VariousWaves_Init:Cannot allocate array InitOut%WaveAcc.
VariousWaves_Init:Cannot allocate array InitOut%PWaveDynP0.
VariousWaves_Init:Cannot allocate array InitOut%PWaveVel0.
VariousWaves_Init:Cannot allocate array InitOut%PWaveAcc0.
VariousWaves_Init:Cannot allocate array InitOut%nodeInWater.

FAST encountered an error during module initialization.
Simulation error level: FATAL ERROR

5

Dear Ioannis,

The MATLAB Toolbox was historically updated to support upgrading FAST input files from v7 to v8 and between various releases of FAST v8. But these tools have not been updated to support the transition to various versions of OpenFAST. That said, the input file changes in OpenFAST have only been small (so far). The input file changes are explained in the OpenFAST documentation here: openfast.readthedocs.io/en/mast … hange.html. The HydroDyn input file has not changed between FAST v8.16 and OpenFAST v2.3. Regarding the airfoil tables, if you have “Ctrl” defined after “Re”, this line is now interpreted as “UserProp”.

Regarding the error you are receiving, this doesn’t seem related to an input file formatting error. It looks like there is not enough memory available in your system to store the data necessary to run your simulation. Do you have a large HydroDyn model with many strip-theory hydrodynamic nodes? Are you perhaps using a 32-bit Windows executable (which limits access to more than 2-GB of RAM)?

Best regards,

6

Dear Jason,

Thank you very much for your detailed reply. Yes the HydroDyn model is large. I used the 32-bit executable since the controller is 32-bit compiled and I cannot use the 64-bit exe. The model could run smooth with FASTv8.16 exe but I got this error when I tried it with OpenFASTv2.3.0

Best regards,
Ioannis.

7

Dear Ioannis,

Perhaps the model requires just about 2-GB of RAM and the OpenFAST v2.3 memory requirements are slightly more than FAST v8.16? You may be able to solve the memory problem by eliminating a few analysis nodes from the model.

Best regards,

8

Hello,
I need some clarification regarding OpenFAST

  1. What is the difference between CompAero and CompInflow in .fst file?
  2. Where is wind force being applied (along the tower or at the hub alone)?
  3. I tried to simulate forced vibration with no wind condition. So, I made CompAero = 0, CompInflow = 1. Then an error message appeared “FAST_InitializeAll:InflowWind_Init:TSFF_ValidateInput: Cannot find TurbSim full-field wind input
    file: 'G:\OpenFAST\Unzipped\openfast-2.3.0\Trial 2\TurbSim\TurbSim.bts”
    During free vibration also, I kept CompAero = 0, CompInflow = 1, In which case it did work perfectly. What could be the possible reason for this?

Thanks in advance

9

Dear Akheel,

Here are my answers to your questions:

  1. CompAero determines how aerodynamic applied loads on the structure are calculated (i.e., which version of AeroDyn is called, or to disable aerodynamic loads altogether) whereas CompInflow determines how ambient wind is defined (i.e., from InflowWind or none (still air)). If you are not computing aerodynamic loads (CompAero = 0), then there is likely no reason to specify wind (so, CompInflow can also be set to 0).
  2. The aerodynamic loads are applied distributed along each blade. If tower aerodynamics are also computed, the aerodynamic loads are also distributed along the tower.
  3. My guess is the path to “TurbSim.bts” wind data file has changed between these two cases.

Best regards,

10

Dear Sir,
Thanks for the response. This message is based on your answer to question 3. If I am simulating no wind condition, Do I need to input CompInflow = 1?

11

Dear Akheel,

Setting CompInflow = 0 will set the wind speed to 0 throughout the domain (still air).

Best regards,

12

Hello everyone,
I have been trying to simulate the forced vibration response for past few weeks. The inputs were given based on a paper which includes: wave spectrum (PM), significant wave height, wave period, wind spectrum (KAIMAL), wind velocity at hub, turbulence intensity. I have tried several combinations of cases for different aerodynamic and hydrodynamic parameters(Eg: TowerPotent, AFAero, etc…), keeping the above inputs unaltered. But the time series obtained are not matching with that in the paper. Can Someone help me where I did mistake?

I got the free vibration plot exactly.

Thanks in advance

13

Dear Akheel,

Well, you haven’t provided nearly enough information so as to pinpoint the problem and solution. Do you get the expected output at least statistically, e.g., mean and standard deviation.

Best regards,

14

Dear sir,
I copied files from r-test to a new folder and input values such as wave height, time period in HydroDyn and .bts file location in Inflow wind file. I used TurbSim to get the .bts file. Wave height, Time period, wind speed and turbulence intensity were the only data which were available from the paper. But the plots am getting is different from the one in paper.
Can I use this platform to share my input files?

Thank you

15

Dear Akheel,

Sharing your files should be the last resort…I’m not sure what to look at because I’m not really sure what issue you are running into. Which paper are you comparing your results to? What is different…time series, statistics, PSDs? Please clarify your problem.

Best regards,

16

Dear Sir,
I referred the paper ‘Coupled modeling and structural vibration control for floating offshore wind turbine’ by Yang et. al, 2020. I plotted the time series for surge under (load case 2 in the paper, Fig 16.a). I have attached a word file in which I have compared surge time series I obtained with the one in the paper. I have been trying to simulate this correctly for around two months. I could not understand where I am wrong.

Thanks
SURGE COMPARISON.docx (311 KB)

17

Dear Akheel,

Well, I’m not familiar with the Yang et al paper, nor with how you’ve set up your simulation, so, I can’t really comment on what is different.

Regardless, the plot you are showing appears to be focused on the start-up transient, rather than the converged solution I would expect that you’d focus on when analyzing a forced vibration response. How does the solution look after all start-up transients decay away (much longer into the simulation)?

Best regards,

18

Dear Sir,
I have simulated a free vibration case with initial fore-aft displacement 10m. Then I incorporated a TMD into it. I could observe that the TMD vibration was shifted. Attached a plot for better understanding.

  1. What could be the probable reason for it.
  2. What do I need to infer if similar behavior is observed in any degree of freedom under wind or wave action
    FreeVibration.docx (707 KB)
19

Dear Akheel,

Regarding (1), are you asking why the heave displacement has a different mean when you incorporate a TMD? My guess is this is related to the increased weight within the system (because of the mass added by the TMD), which you have not compensated for in the floating wind turbine by increasing the static buoyancy or reducing the mooring pretension.

Regarding (2), I’m not sure I understand your question.

Best regards,

20

Dear Sir,
Regardiung (2), I meant that if I see similar behavior (shift in mean position) for any dof (not necessarily Heave) under wind and wave, Will it be due to increased draft?