HydroDyn altered for up to fifth harmonic forces

[David-Coyne-Github]

Hi all,

I'm currently an undergraduate completing a dissertation for my university degree; as part of this dissertation, I would like to contribute to the OpenFAST program based on recent research in the field.

The HydroDyn program allows for the first and second harmonics to be calculated. However, recent research (Chen et al, 2018) suggests that for some wave states, up to 60% of the forces are non-linear (Page 73). This is to say, forces related to harmonics 2-5 may contribute more than anticipated currently, and further development may benefit future design.

I would like to develop HydroDyn according to the equations developed by Chen et al in 2018 - which have thus been supported by laboratory tests - so as to generate more accurate forces on turbines.

Is this something that is feasible for the OpenFAST project? Furthermore, how would you recommend beginning this endeavour?

Thanks for any help you are able to give. Please find reference to the paper I have mentioned below:

Chen, L.F. et al. (2018) “An experimental decomposition of nonlinear forces on a surface-piercing column: Stokes-type expansions of the force harmonics,” Journal of fluid mechanics, 848, pp. 42–77.

[jjonkman]

Dear @David-Coyne-Github,

NREL generally encourages community contributions to the source code. And I agree that introducing options that support higher degrees of hydrodynamic linearity are important development pathways.

General guidance for further development of the OpenFAST source code is provided here: https://openfast.readthedocs.io/en/main/source/dev/index.html. I would encourage you to familiarize yourself with this process.

Given that you are proposing significant hydrodynamic changes and HydoDyn is changing extensively between the current main release of OpenFAST and the upcoming v4.0 release (including the introduction of the new SeaState module that has been separated from HydroDyn: #1008), I would encourage you to start with the existing dev branch of OpenFAST (which contains SeaState) rather than with main.

It may also help to schedule a brief call with the OpenFAST team (including @luwang00) to discuss the approach before moving forward.

Best regards,

[David-Coyne-Github]

Hi @jjonkman,

Thank you for the swift response! I will look at the dev version so as to incorporate seastate too. What is the current schedule for v4.0 with regards to its release? Depending on time-scale (I am unaware of how many weeks/months/years these projects usually take), it may be possible to include up to the fifth harmonic in that release.

I would greatly appreciate a call as you recommended. What platform would this be best to engage on?

Kind regards,

[jjonkman]

Dear @David-Coyne-Github,

We are hoping to release OpenFAST v4.0 in the next month or two, so, I doubt your changes could be included with that release. But your changes could be included in a future release.

Let's move the discussion around a possible call to an e-mail discussion. Please e-mail me directly.

Best regards,

[David-Coyne-Github]

Hi @jjonkman,

I cannot appear to find your email on your profile. What address would you prefer me to contact?

Kind regards,

[jjonkman]

Dear @David-Coyne-Github,

See: https://www.nrel.gov/research/staff/jason-jonkman.html.

Best regards,