Questions about wave direction
Hello everyone,
I utilized NEMOH to compute the hydrodynamic wave excitation of the OC4_Semisubmersible in the test cases and compared it with the results in the OpenFAST test file, calculated using WAMIT. The subsequent figure illustrates the first-order wave excitation force in the surge direction for wave incidence angles of -180 degrees and -150 degrees, respectively. As depicted in the figure, while the magnitudes match well, the phase angle exhibits symmetry about 0 degrees. It seems that the wave excitation force computed with NEMOH differs by exactly 180 degrees from the results obtained through WAMIT.
These are the corresponding NEMOH input files and the result files based on WAMIT calculations.