October 23, 2022 at 4:08 pm

Geovanna Quinde

Subscriber

Hello Peter, thank you for your reply. This is the section the ship, this geometry is between two watertight bulkheads (bulkheads are not included) and two decks (decks not included). Because of symmetry we did just one side.

We try to simulate the vibration produced by onboard machinery and see the response of this vibration in the geometry. To include vibration, we thought we could include it as a displacement.

- Playing around with the program we realized that we can’t include a displacement when using the mode superposition method.
**Why is this happening?**

So we did a full harmonic solution method, and we saw that Displacement and Nodal Displacement can be applied.**What is the difference between them?** - Then, we applied a Nodal Displacement of 2.5 mm, but we are not sure about what displacement we can enter,
**Do you have some references to see what amplitude of displacement is okay?** - For a full harmonic solution method, we include a constant structural damping coefficient, but while looking for some reference values we found a longitudinal loss factor,
**are they the same? Or we can just double the viscous damping ratio?** - These are the boundary conditions for the geometry, we are going to consider to expand this geometry since applying fixed supports in the borders near the region of interest, will affect the asnwer.
**Do you have any recommendation for boundary conditions?** - We have seen that in harmonic module it is included some boundary conditions,
**are they for the whole geometry or for some sections where the vibration is located?** **Finnally, the way we consider to simulate the source of vibration is the adecuate or it is better to consider a force?**