I am working on comparing the experimental results from model tests of a FWT with the numerical results from OpenFAST. Because I am interested in looking at second-order responses and the necessary input files for the potential flow solution are not available in the literature, I had to develop my own hydrodynamic analysis. For the hydrodynamic frequency domain analysis I used AQWA and then translated into the WAMIT format using BEMRosetta.

I think my HydroDyn input file is okay and looks like this:

The error message I get is the following:

…"Calculating second order difference-frequency force using the full quadratic transfer function.

FAST_InitializeAll:HydroDyn_Init:WAMIT2_Init:DiffQTF_InitCalc: The second order WAMIT data in

.../HydroData/AQWA_model_FQTF/Analysis.12d is too sparse for the

interpolation routine used in the full Difference QTF calculation. At some later point, we will

allow for sparse data when a different interpolation routine is implemented.

OpenFAST encountered an error during module initialization.

Simulation error level: FATAL ERROR

Aborting OpenFAST. "…

I am wondering why this could be, what does it mean?

In my hydrodynamic model, I followed the suggestions and recommendations from section 4.2.8.4.8.4. in 4.2.8.4. Modeling Considerations — OpenFAST v3.5.1 documentation : The discretization of the set of directions is fully populated (not sparse), with a range of [-180:10:180]. Also, my frequencies span the range of [0.25:0.05:2.75] rad/s.

Thanks,

Tomas.