Learning Forum

[M. Namaki]

Dear َANSYS community,

I'm currently working on a simulation in ANSYS AQWA (2023 R2) and have encountered two persistent issues that I’d like to better understand and resolve.

1. CONVOLUTION WARNING – Inaccurate Convolution Fit

I receive repeated warnings such as:

"CONVOLUTION WARNING. An inaccurate convolution fit has been detected to the added mass/damping for structure #X/Y Surge(X)/Pitch(Y) for frequency #50. The fit quality was ~30% (or sometimes even more). This can be caused by insufficient frequencies or an unusual geometry of the structure. PLEASE - ENSURE THAT THERE ARE SUFFICIENT FREQUENCIES BEFORE contacting user support. Frequency range should be at least 0.077 to 2.603 rad/sec."

I’ve noticed that when I change the frequency range in the Hydrodynamic Diffraction module to fall within the recommended bounds (e.g., 0.077 to 2.603 rad/s), this warning doesn't disappear. However, I’m looking for a way to first understand where does this problem's roots come from and to eliminate or minimize this warning (even without changing the frequency range if it's possible, by modifying input parameters instead). Could anyone advise what model settings or inputs can be adjusted to improve the convolution fit quality?

2. "JACOBI: Failed to Converge" Warning

Additionally, I receive the warning:

"JACOBI: Failed to Converge."

This appears during the simulation, but the documentation does not provide much context. I would appreciate any insight into what causes this issue and how to resolve it. 

I need to add that the simulation involves multiple hydrodynamically interacting structures. the project completes successfully despite the warnings, but I would prefer to clean up these issues for better accuracy.

Any advice or suggestions from experienced users would be greatly appreciated.