Trans RINA, Vol 157, Part A3, Intl J Maritime Eng, Jul-Sep 2015
Assuming the grounding damage scenario shown in Figure 3, for the full loading initial condition, the final equilibrium after flooding was obtained both from the developed simulation and from Autohydro. In Table 4 is reported a comparison between the results obtained by applying the two aforementioned approaches.
Table 4. Bottom damage, final equilibrium comparison: hydrostic code (Ahydro) vs time domain simulation.
Flooded water Initial trim Final trim Initial z Final z
Variable Ahydro 612.2 t 0°
-3.13°
-2.856 m -1.919 m
Simulation 611.6 t 0°
-3.125° -2.856 -1.920
As could be noticed the comparison shows a good agreement regarding the final stage of equilibrium after flooding. In performing the dynamic simulation in the developed code, an effective damage hole of 3 m2 was assumed located across the damaged compartments. The head of water, in evaluating the hydrostatic head of water, was obtained as the mean value of the pressure at the ship bottom, in the zone of the damage hole. The time domain results for the simulation, reported in Table 4, are shown in the next section in Figure 12.
The numerical simulation is intended for analysing the effect of water trapped in compartment characterized by high free-surface moments. For checking the capability of the system to deal with negative GM conditions, the angle of loll was evaluated within the simulation and compared with Autohydro results.
Figure 9. Intact ship in wave simulation. 5. INTACT SHIP DYNAMIC BEHAVIOUR
In this section the calculations regarding the behaviour of the intact ship in wave are presented; the results obtained by the implemented non-linear simulation for the intact ship are checked, before applying the damage analysis.
This check was performed by comparing the non- dimensional
responses obtained Figure 8. Loll simulation.
The amount of water trapped in the garage was set to a sample value of 50 t corresponding to 0.086 m of water on the deck, for the ship in even-keel position. From the hydrostatic computation the vessel shows a negative
©2015: The Royal Institution of Naval Architects from the numerical
simulation, for several wave frequencies and amplitudes, with linear seakeeping responses (Faltinsen 1990). The heave and pitch comparisons are shown respectively in Figure 10 and 11.
The carried out comparison shows a good agreement between the developed method and the linear seakeeping results.
metacentric height i.e. GM=-6.384 m, that leads to a loll angle of 7.84°, together with a trim angle of 0.05°.
In Figure 8, the time domain results from the developed simulation model are presented. The final equilibrium results are respectively 7.653° for the angle of loll and 0.042° for the trim angle due to the loll. Also in this case a good agreement with the known hydrostatic code was achieved.
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