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Hull dynamic pressures

Hydrodynamic pressures transfer functions (RAOs) are direct output results of any diffraction/radiation software package. A diffraction/radiation analysis requires a mesh of the floater 's hull as input data and pressures are calculated on each panel of the mesh.

  • For coupled analysis with DeepLinesTM, only global hydrodynamic terms are used; They result from the integration of the hydrodynamic pressures over the whole hull and are stored in the HDB file.

  • In case of a sub-structures approach, the integration shall be partially performed on different members of the hull to get the global forces acting on every sub-structure.

For recent analysis of floater's structures like wind turbines floating platforms, it turns out that it would be of valuable interest to retrieve dynamic pressures time series once a coupled anlaysis provides the floater's motions.

That's the reason why, this specific post-processing module has been implemented allowing to compute the different terms of the dynamic pressure from any coupled analysis provided the diffraction/radiation analysis has been performed with Diodore and that the non-linear Froude Krylov option has been selected. Actually, the computation of hydrodynamic pressures requires more detailed output data from the hydrodynamic computation than the data provided in the HDB file.

Along with the HDB file, the following files generated by Diodore must be available otherwise the "hull dynamic pressures" post-processing will fail:

  • file_root05.DAT : (sub)structure mesh definition wrt the global mesh
  • file_root06.DAT : mesh refinement near sea level
  • file_root15.DAT : mechanical parameters (inertia, CoG, reduction point...)
  • file_root16.DAT : hydrodynamic parameters
  • file_root30.DAT : diffracted/radiated pressure fields
  • file_root98.OUT : hydrodynamic modelling assumptions
  • ELM9999.DAT : mesh connectivity

These files are generated by Diodore with a specific file root which must be introduced in the floater motion type as illustrated below:

The theoretical background for the hull dynamic pressures computation may be found in hydrodynamic pressure.

In the same way as for fatigue analyses, a "Hull dynamic pressures" analysis is seen as a global post-processing that may applied on several analyses attached with your model and previously run.

This is the reason why a specific folder is displayed in the Model browser dedicated to the management of various "hull dynamic pressures" analyses.

This Section provides details on the following :