Turbulence doesn't play a role

[Chengyue810]

When I was trying to calculate the frequency domain response of raft, I found that the wind field's profile power index and turbulence intensity had no effect on the results, which is inconsistent with common understanding. I would like to ask if this is normal for raft? Perhaps it focuses more on waves and ignores the influence of the wind field.

[lucas-carmo]

Hi @Chengyue810

You're correct, RAFT currently does not account for the frequency-dependent aerodynamic loads induced by turbulent wind. The capability is there but it is currently commented out (see https://github.com/WISDEM/RAFT/blob/1a25f980479fa4b902ccbecf915bd94da6d13a9a/raft/raft_model.py#L1091) because there's something wrong. We've found some bugs recently but the problem isn't fully solved yet, so we're still working on it.

[Chengyue810]

@lucas-carmo Thank you. I found the problem you mentioned when I was studying the source code today. I guess there may be a problem with the transmission of the wind spectrum function. I am currently studying how to modify it. Thank you very much for your contribution.

[lucas-carmo]

Sweet, thank you! I hope you can find what's going on 😁

Btw here's the commit with the recent bug fixes that I mentioned: c8b1f3a
That change will be released in v1.5.0, which should be out later today.

[kasia129]

Hi RAFT team,

Just wanted to check whether you plan any changes to the frequency-domain aerodynamic loads model/rotor excitation, or if that work is parked for now? Referring to the block of code in raft_model.py:

# rotor excitation
        '''
        F_rotor = np.zeros([self.nDOF, self.nw], dtype=complex)
        
        for i, fowt in enumerate(self.fowtList):
            F_rotor[i*6:i*6+6] = np.sum(fowt.f_aero, axis=2)
            
        for iw in range(self.nw):
            self.Xi[-1,:,iw] = np.matmul(Zinv[:,:,iw], F_rotor[:,iw])
        '''

Thanks,
Kasia

[lucas-carmo]

Hi @kasia129

I think (or rather hope) this issue was fixed in the dev branch (see this bug fix 3edf6eb courtesy of Gijs Bouman) but we haven't had time to test it yet. Please feel free to give it a try and let us know how that goes!!