I am trying to understand what exactly occurs within the code when hydrodynamic and atmospheric loads are coupled.
It seems from what I have acquired, that they are coupled but how is the spectra modeled in conjunction with the other load (wind or wave)?
Since it may be more of a general question, do you know where I can find more information about this topic?
Furthermore, it seems there is no way to model corrosive damage to the structure correct?
Your first question has been discussed on our forum before–see the following forum topic: http://forums.nrel.gov/t/meteorological-codes-for-offshore-conditions/275/1.
Modeling corrosive damage would imply a change in structural properties (e.g. mass and/or stiffness) over time. This damage would not occur instantaneously such that changes in mass and/or stiffness would need to be considered over the course of a given simulation, which is typically 10 minutes or so in length. Instead, the effect of mass and/or stiffness changes can be realized by setting up different input files characteristic of each damaged state to be considered.
Thank you for the advice.
Furthermore, when coupling hydrodyn and subdyn, they both seem to have displacements and rotations output for the foundation structure.
Do you know what exactly is the difference between the two outputs?
Are you referring to outputs WRPSurge etc. in HydroDyn and IntfTDXss etc. in SubDyn? In HydroDyn, output WRPSurge is the X-component of the translational displacement of the WAMIT reference point whose origin is always (0,0,0). In SubDyn, output IntfTDXss is the X-component of the translational displacement of the transition piece (platform) reference point, whose origin is (0,0,PtfmRefzt), where PtfmRefzt is specified in the ElastoDyn input file. (Likewise for the other 5 outputs.) Because the motion of the WAMIT reference point and transition piece come from the same source (ElastoDyn), while the rotation outputs between HydroDyn and SubDyn should always match, the translations will differ unless PtfmRefzt is zero.
I hope that helps.
That was very helpful,
thank you for the clarification!