This load case is similar to OC4 P2 LC3.3, but the wind and wave loading is much more severe in this case (Vhub=47.5.0m/s rather than 18.0m/s, and Hs=15m rather than 6m). The simulation actually failed to complete in Flexcom due to an error in the InflowWind module. The turbulent wind field input data files were originally created by DTU (Technical University of Denmark) and kindly passed on to us by NREL. The vertical extents of the wind field definition are 17.46m and 162.54m respectively above still water. Given the severity of the applied loading, the induced platform motions causes one of the blade nodes to pass below the lower boundary of the wind field definition at a certain point during the simulation. InflowWind is unable to compute the wind velocity at this point so the software issues an error message and terminates: "FF wind array boundaries violated. Grid too small in Z direction (height (Z=17.401 m) is below the grid and no tower points are defined". It would be possible to manually regenerate the turbulent wind field with larger boundaries using a third-party wind turbulence simulator, but we wanted to use the exact wind field definition used by the OC4 participants to ensure consistency of the Flexcom model with the others. We are not sure if any of the other participants experienced a similar problem or not, as the load case is not discussed by Robertson et al. (2014).
