This example implementation of the fully coupled wind solution in Mechanical APDL follows a similar strategy to that used for ASAS. In particular, data access is provided through the same set of interface routines. This enables easy adaptation of the new facility by existing ASAS wind turbine users.
The following summarize the modeling characteristics in Mechanical APDL for a wind coupling analysis:
The turbine effect is modeled via the user element USER300. This special user element has 9 nodes, with 6 freedoms (UX, UY, UZ, ROTX, ROTY, and ROTZ) on the first node and 3 freedoms (UX, UY, and UZ) on each of the subsequent nodes, making it capable of having a maximum 30 degrees of freedom on the element. The first node is the connection point between the turbine and the supporting structure and therefore it must be a node in the structural model. The other 8 nodes are created to accommodate the additional freedoms that are internal to the turbine element and are used solely by the aeroelastic code. Therefore, these nodes should not be connected to any other parts of the model.
Key option 1 (KEYOPT(1)) of the user element is used to specify the damping matrix option. Damping can be obtained from the aeroelastic code alone, or computed from Rayleigh damping in Mechanical APDL based on the turbine mass and stiffness matrices, or both. KEYOPT(1) = 0 indicates that the damping matrix will be taken from the aeroelastic code plus Rayleigh damping, and this is the default. KEYOPT(1) = 1 indicates that only Rayleigh damping will be used. KEYOPT(1) = 2 indicates that only damping from the aeroelastic code will be used.
The element does not have any material property or real constant data.
The element mass will not generate any body forces even if accelerations (e.g. ACEL) are defined.
The only element results available are the element nodal forces.
A Mechanical APDL command macro called WTBCREATE is provided to assist with the creation of a wind turbine model. This will automatically generate a turbine element and issue relevant data commands that are necessary to run a wind coupling analysis.
Special versions of the user subroutines
UserElem,USolBeg,USsFinandUSolFinare provided to enable a wind coupling analysis. In addition, the shared common DLL WTBFunctions.dll is also required. A custom build of Mechanical APDL is required during which the aeroelastic linking option should be selected.The analysis type should be transient (ANTYPE, TRANS) for a wind coupling analysis.