Shuangxing Du
Ansys Employee

(1) If your mooring line is not a nonlinear catenary cable

 You may not need to define Structure A. Instead, just define a fixed point, and link Structure B with this fixed point by your mooring line.

(2) If your mooring line is a nonlinear catenary cable

By using the similar approach of defining Structure B (Buoy), you can define another structure (Structure A) from Geometry then share the geometry with the Hydrodynamic Diffraction analysis.  In Aqwa Editor in Workbench, set Structure Fixity of the Structure A  as "Structure is Fixed in Place", define the connection point on Structure A and a fixed point, define a rigid joint with these two points to link Structure A and the fixed point for the Hydrodynamic Response analysis. Another pair of the connection points should be defined on Structure A ans Structue B for setting up your catenary mooring line. 

In Hydrodynamic Diffraction analysis, if the hydrodynamic interaction between Structure A and Structure B needs to be considered, these two structures should be in an Interaction Structure  Group.

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