Ansys Learning Forum › Forums › Discuss Simulation › General Mechanical › AQWA Eigenvalue vs Free Decay Test Resulting in Different Heave Natural Period? › Reply To: AQWA Eigenvalue vs Free Decay Test Resulting in Different Heave Natural Period?

July 5, 2023 at 8:33 pm
riyanto.r
Subscriber

Hi Mike, thank you for your clear explanation! I am surprised that AQWA can process the non-linear stiffness from the structure; I should read the documentation more deeply! 

However, I have several follow-up questions:

  1. How can the solver get the non-linear hydrostatic stiffness above the waterline of the structure if we only included the wetted area during the hydro-diffraction analysis? I excluded the freeboard structure above the waterline (to avoid error). Is there any setting(s) that I should have included here?
  2. During the time-domain analysis of the no-wave decay test, how does the solver calculate the added mass & damping ratio? Is this term fixed? Therefore they read the added mass coefficient from the diffraction analysis at its respective natural period? Because added mass & damping is dependent on the wave period. I would like to know what coefficient the solver chose if no wave is included in the simulation. 

Thank you!
Danu Riyanto