Platform Added Mass (PtfmAM) Matrix

Wind & Water Computer-Aided Engineering Software Tools
1

Hello,

I am having trouble adding a platform to my turbine model… I am getting an “Rzero needs to be less than 1 error”. I am trying to debug all sources of issues with the platform. I am wondering if the Platform Added Mass (PtfmAM) matrix has something to do with this. Could this be part of the problem? Right now my PtfmAM matrix is a 6x6 matrix that is populated with zeros. What is the purpose of this matrix? When is it used? Should I populate this matrix in FAST prior to running a simulation? If so, what would be the values that I would use to populate the matrix? If not, does the matrix get populated as the simulation runs?

Much thanks,
Colin

2

Dear Colin,

I’m assuming you are trying to implement your own UserPtfmLd() routine? The comments at the top of the subroutine provide some guidance. What sort of physics are trying to model with this routine?

PtfmAM is a 6x6 added-mass matrix of the platform. The matrix should be populated with any terms needed for properly defining platform-acceleration-dependent loads, such as hydrodynamic added mass for floating platforms, or soil added mass for fixed structures. The matrix should not contain body mass/inertia terms associated with the platform structure, which are already accounted for with FAST inputs PtfmMass, etc. The matrix can be zero if there are no platform-acceleration-dependent loads.

Best regards,