4. Vibratory analysis of a wet structure: spectral approach

From the modal base of the wet structure and the modal excitation inter-spectrum calculated in PROJ_SPEC_BASE, the user can directly proceed to calculate an inter-spectrum of generalized displacements by means of the operator DYNA_SPEC_MODAL. Here the user is also required to enter the flow speed if the modal base is of the melas_flu type, and can choose to calculate the entire inter-spectral matrix of the generalized displacements or else only the diagonal terms (the auto-spectra).

To return the generalized results on a physical basis, the user must then use the operator REST_SPEC_PHYS. He can then calculate for example an inter-spectrum of movement on one or more nodes, for the components of interest (\(\mathit{DX}\), \(\mathit{DY}\), \(\mathit{DRX}\), etc.). If the aim is to calculate the RMS values, the resulting inter-spectra are to be post-processed by the POST_DYNA_ALEA operator.