For clarity, the correct coefficients are shown below: In light of this mistake, the supporting OrcaWave and OrcaFlex models have been corrected, and the latest version of the example is now available for download from the usual L Diffraction examples page of the Orcina website. This difference in units was not accounted for as part of the model building process, which led to the transfer of incorrect coefficients to the ‘Other damping’ page of the OrcaFlex vessel type data form. Those tests used damping coefficients with force units of newtons (N), however, the example models uses units of kilonewtons (kN). The coefficients were then calibrated in OrcaFlex, through a series of free-decay tests. To explain the problem, the original damping coefficients were referenced from a comparison study against tank test results, documented as part of the Offshore Code Collaboration study OC6 project – Phase I. We have recently identified an issue with the L02 OC4 semi-sub example, where incorrect linear damping coefficients were used as input to the semi-submersible model.
