Dear All,
I am currently working on a hybrid wind–current energy system by coupling two RM1 tidal turbines with the NREL 5 MW wind turbine supported by the OC3 Spar platform. In my model, the two RM1 turbines are mounted horizontally on opposite sides of the spar at z = -50 m.
To the best of my knowledge, OpenFAST does not support horizontal towers directly. Therefore, I modeled the supporting structures as two Morison members in HydroDyn at z = -50 m, while assigning the corresponding ElastoDyn towers a negligible height. Specifically, TowerHt and TowerBsHt are set to -50.1 m and 50 m, respectively, so that the tower geometry has minimal influence on the model.
However, I encountered an issue with the visualization in ParaView. When NacCMzn, NcIMUzn, and Twr2Shft are all set to 0 m, which should place the RM1 nacelles in line with the Morison members at z = -50 m, the nacelles do not appear in the visualization. Interestingly, if these three parameters are instead set to -1.2 m (i.e., slightly below the expected position), the nacelles are displayed correctly.
Has anyone encountered a similar issue, or could you suggest what might be causing this behavior? Any suggestions or insights would be greatly appreciated.
Best regards,
Shang Liu
Dear @Shang.Liu,
Presumably you are using the new multi-rotor functionality available in OpenFAST v5; is that correct?
That said, currently, a user must specify either a wind system or a marine hydro-kinetic (MHK) system; not both. So, I’m not sure how you are modeling the NREL 5-MW baseline wind turbine along with two RM1 tidal turbines; can you clarify?
In the multi-rotor capability, the multi-member support structure should be modeled in SubDyn given that in ElastoDyn the tower is limited to a single vertical monotower configuration. Do you have SubDyn enabled?
FYI: We have discussed supporting hybrid wind and MHK turbine systems, but this would require having two instances of AeroDyn–one for the wind turbines and one for the water turbines, but we have not developed such functionality yet.
Best regards,
Dear Dr. Jason,
Thank you very much for your clarification and suggestions.
Yes, I am currently using OpenFAST v5.0, including the new multi-rotor functionality.
Regarding the hybrid wind–current energy system, I understand that the current version of OpenFAST does not support having both a wind turbine system and a marine hydrokinetic (MHK) turbine system in the same simulation. Therefore, at this stage, I am not attempting to simulate the complete hybrid wind–current system simultaneously. Instead, I am currently developing and validating a model consisting of the OC3-Hywind Spar platform with two RM1 MHK turbines mounted horizontally on opposite sides of the spar.
Regarding the support structure, I have indeed enabled SubDyn and modeled the supporting structures using SubDyn. I have attached the SubDyn input file SubDyn.dat and a schematic of the model configuration for reference.
I would greatly appreciate it if you could take a look at the SubDyn configuration and let me know whether this is an appropriate way to model the two horizontal support structures within the current multi-rotor framework.
Thank you again for your guidance.
Best regards,
Shang Liu
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Dear @Shang.Liu,
Yes, I agree with how you formulated your SubDyn input file for this case.
Regarding your original question, I believe the visualization of the nacelle from ElastoDn is tied to the difference in hub and tower-top reference positions, so, I could foresee it not showing properly when Twr2Shft is zero.
Best regards,
