convergence issue in the mechanical side of a FSI problem

- April 3, 2020 at 4:11 am
  
  azing
  Subscriber
  
  Hello,
  
  I am simulating the behavior of a building in two perpendicular directions through nonlinear springs that are attached to a rigid box (please see the attached figure). The box is located on a spherical joint.
  
  I intend to couple this model with Ansys Fluent later on to take into account FSI using system coupling capability in workbench. That is why I chose flexible behavior for the box (since rigid surfaces were not accepted as valid options for FSI). However, in order to get rigid behavior, I increased the modulus of elasticity of the flexible body.
  
  I am now not able to get convergence in Transient structural and I think it is because of the rigid motion of the box since I get the warning "not enough constraints ... to prevent rigid body motion".
  
  I don't understand why it is not converging since I don't have a problem in the modal and static analyses. I would appreciate it if any one can help me with this.
  
  Thanks,
  
  Azin