Structural dynamic model: Obtain forces on the rotor

Wind & Water Structural Analysis
1

Hi !

We are developing a code for structural dynamics of the tower and substructure, based on a numerical method different from that used by FAST. An input parameter in the code is given by the forces on the rotor and tower, which will be applied in transient analysis of the structure.

The reason for this development is the consideration of different analysis options, such fluid-structure and soil-structure interaction, and features such as physical and geometrical nonlinear analysis, in addition to other specific options of a code dedicated to structural analysis.

The intention is to integrate this code with some of the components of the FAST modular structure, which will be applied to the computation of aerodynamic loads.

<<< Questions >>>

  1. Is it possible to obtain the forces on the rotor and tower without performing a full analysis in FAST,
    avoiding processing the complete set of modules? That is, using only aerodynamic and control modules, such as AeroDyn and ServoDyn, plus ElastoDyn for blades and nacelle?

  2. Consideration of rigid properties for the tower and substructure is a viable alternative if a full analysis is required? Is this the simplest alternative?

Thanks.

2

Dear Carlos,

You can enable/disable all modules of OpenFAST except ElastoDyn, which must currently in FAST/OpenFAST must always be enabled. However, you can disable features of ElastoDyn that you don’t want enabled. For example, if you want to model a rigid support structure, you can disable the platform and tower degrees of freedom (DOFs) in ElastoDyn; you can also set the mass and stiffness of the platform and tower to zero (or near zero) if there associated DOFs are disabled.

Are you planning to implement a two-way coupling between FAST/OpenFAST and your new structural code? If so, then you would likely need to establish a coupling in OpenFAST similar to what currently exists in the ElastoDyn-SubDyn coupling, i.e. 6-DOF motion (i.e., the platform DOFs in ElastoDyn, including position/orientation, velocity, acceleration) is passed from ElastoDyn to SubDyn and 6-DOF loads (forces, moments) are passed from SubDyn to ElastoDyn at each coupling step. Are you setting up your new structural code to support such a coupling?

Best regards,

3

First of all, sorry for my delay.
And thank a lot for your fast answer.
I’m creating a separate code in matlab for structural analysis. And aerodynamic coupling.
I am not using open fast because my code was not written em fortran. So, I just use FAST for aerodynamic and hydrodynamic load

Best regards