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OpenFAST / openfast

Main repository for the NREL-supported OpenFAST whole-turbine and FAST.Farm wind farm simulation codes.
http://openfast.readthedocs.io
Apache License 2.0
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When I was calculating a 15MW wind turbine, I wanted to explore the effect of ocean currents on the turbine, but the test results were less than satisfactory #2061

Open lin990316 opened 9 months ago

lin990316 commented 9 months ago

In the case of the 15MW floating wind turbine, the platform response does not seem to be obvious after I introduce the sea current compared with the environment with no wind and no waves. Under the rated wind speed of 10.59m/s condition, I set the wave height of 4.9m, and after the introduction of the sea current, despite the obvious increase in the surge, the calculation result is almost exactly the same regardless of the setting of the speed of the sea current, and regardless of the angle of the sea current, may I ask if this is a normal situation? In addition, I didn't understand the three modes of currents in HydroDyn in the user's manual. Are these three modes independent of each other, and should I choose one of them to set the velocity and direction of the currents in the calculation, or are all three current models used in the FAST calculation at the same time?

jjonkman commented 9 months ago

Dear @lin990316,

Are you using the IEA Wind 15-MW reference wind turbine model atop the UMaine semisumbersible from the following repository: https://github.com/IEAWindTask37/IEA-15-240-RWT/tree/master/OpenFAST/IEA-15-240-RWT-UMaineSemi?

The sea current functionality of HydroDyn works in conjunction with the viscous drag calculation of the strip-theory members. However, the aforementioned OpenFAST model does not have any strip-theory members; rather, viscous effects are captured through a simplistic approach, lumping the contribution of viscous effects into an AddBQuad matrix. Unfortunately with this approach of capturing viscous effects, enabling sea current in HydroDyn will not influence the floater response (which is not correct). In general, it is better to capture viscous effects through strip-theory members.

I'm not sure I fully understand your second question, but the current modeling options of HydroDyn are documented here: https://openfast.readthedocs.io/en/main/source/user/hydrodyn/input_files.html#current.

Best regards,

lin990316 commented 9 months ago

Dear @jjonkman Thank you Dr for your answer, I am using exactly the model you mentioned, “ it is better to capture viscous effects through strip-theory members. ” Regarding the method you are talking about I don't understand it very well, do I need to implement it by means of modifying the source code, i.e. I can't study the effect of currents on the response of the turbine if I just use the existing FAST software and model? thanks again

Best regards,

jjonkman commented 9 months ago

Dear @lin990316,

A source code change is not needed to fix this.

Instead, the HydroDyn input file for this OpenFAST model should be changed so that viscous effects are handled through the strip-theory solution rather than through AddBQuad. My understanding is that such an OpenFAST model already exists for this reference system, but I'm not sure if that model is hosted publicly. This is probably a better question to ask in the IEA Wind 15-MW reference wind turbine repository: https://github.com/IEAWindTask37/IEA-15-240-RWT/issues.

Best regards,