Dynamic external loading on the turbine

Wind & Water Rotor Aerodynamics
1

Hi Everyone,

I am a PhD student.

I am trying to develop a surrogate model to replicate the aerodynamic force of the Floating wind turbine, I need to introduce the output of my surrogate model instead of the aerodynamic load in the Openfast to see how the error due to my surrogate model will effect the response of the platform.

My surrogate model is based on position, speed and acceleration in different degrees of freedom and wind speed time history, and it will provide an estimation of what thrust might be.

For that purpose, I started using the Extload (Num3) of the CompAero module (subroutine ExtLd_CalcOutput). But I don’t know whether I chose a good place or not, or am I doing it correctly or not. I saw an option that I can apply the force directly to elastodyn but I guess it works with time histories. (https://forums.nrel.gov/t/disable-aerodynamic-forces-in-some-directions/2863?u=amirhossein.ghareh ). I also saw Dr Jonkman said (https://forums.nrel.gov/t/dynamically-imposing-forces-on-a-floating-platform/9007/4?u=amirhossein.ghareh ) in Discon controller we can do something. Can you advice on it?

And additionally I want to apply the force as a single point load on the hub. Right now, since I couldn’t find the hub position, I apply it on the highest point of the tower.

“ y%TowerLoadAD%Force(:,1) = 0.0_ReKi

y%TowerLoadAD%Force(1,1) = thrust ”

When I run the program, it does the mooring settlement and then immediately after that, it prompts an error showing that simulation failed. Please see the error below:

“Parsing MoorDyn input file: .\IEA-15-240-RWT-UMaineSemi_MoorDyn.dat

Warning: invalid output specifier FX. Object ID missing.

Warning: invalid output specifier FY. Object ID missing.

Warning: invalid output specifier FZ. Object ID missing.

Created mooring system: 3 lines, 6 points, 0 rods, 0 bodies.

Finalizing initial conditions using dynamic relaxation.

t=0.1 FairTen 1: 2.04083E+06, 1, 2 t=0.2 FairTen 1: 2.48971E+06, 2.04083E+06, 1 t=0.3 FairTen 1: 2.61091E+06, 2.48971E+06, 2.04083E+06 t=0.4 FairTen 1: 2.60906E+06, 2.61091E+06, 2.48971E+06 t=0.5 FairTen 1: 2.53340E+06, 2.60906E+06, 2.61091E+06 ………………………..

………………………..

t=26.4 FairTen 1: 2.44744E+06, 2.44583E+06, 2.44321E+06

… Output truncated. Text exceeds maximum line length for Command Window display.

The following simulations failed”

When I use Aerodyn module, it is working fine, but I don’t know why when I use “extload” this error shows up.

2

Dear @Amirhossein.Ghareh,

I’m not familiar enough with ExtLoads, which is the module OpenFAST uses to couple with CFD to know how simple it would be to modify for your use case.

Can you clarify: Does your aerodynamic surrogate model lump all rotor aerodynamic loads to a single point (at the hub), such that you plan to model the blades rigidly? If, so, it may be easiest to start with the AeroDisk module of OpenFAST and modify it for your use case.

When I was reading your message, I originally thought of you customizing the Structural Control (StC) submodel of ServoDyn, but while this module allows you to prescribe loads on the blades, nacelle, tower, and substructure, there is no direct coupling between StC and the ElastoDyn hub. But perhaps the nacelle is a reasonable substitute for the hub (probably not if you want want to keep GenDOF enabled in ElastoDyn)? A workaround would be to take your hub loads, split them into 3, and apply 1/3rd to each blade through StC, but that would add a bit of extra complication.

Best regards,