Trans RINA, Vol 154, Part A2, Intl J Maritime Eng, Apr-Jun 2012 Equilibrium Water Level as a function of Heel Angle 60 Model Fully Constrained
Heel Angles: Positive to Starboard Regular Beam Seas
50
Nominal Wave Height = 50mm Nominal Wave Frequency = 0.9Hz
40
30
20 10
2Aft-S11 Calm Water 2Aft-S11 Regular Beam Seas 2Centre-S12 Calm Water 2Centre-S12 Regular Beam Seas 2Centre-S15 Calm Water 2Centre-S15 Regular Beam Seas 2Fwd-S16 Calm Water 2Fwd-S16 Regular Beam Seas
0 -1
0 123 4567 89 Heel Angle (degrees)
Figure 15 Equilibrium water level as a function of heel angle 10 11
6
CONCLUDING COMMENTS
A series of experiments has been conducted in calm water and regular beam seas on a 3.268 metre long model of a generic destroyer hull form to investigate the progressive flooding in a complex geometry in order to further validate the progressive flooding model in a non- linear time domain ship motions code. With the model fully constrained, a rapid damage event was generated, and the water levels and pressures in some of the internal compartments measured, as functions of time.
The effect of the area of the damage opening was investigated by conducting calm water tests with damage opening extents ranging from 50% to 100%. When the damage opening was only 50% the rate of rise of water in each of the compartments on the 2nd Deck was slower than for the greater damage extents. The results for the case with 85% damage opening were similar to those for the 100% case, with the greater damage extent generally resulting in only a marginal increase in the rate of water level rise.
This may be worth further, more systematic,
investigation. Tests were
also conducted with the model fully
constrained in regular beam seas. The incident waves caused the water levels in the tanks to oscillate, with the oscillation levels greater in magnitude on the starboard side (nearer the damage) than on the port side.
Of particular note, there appears to be a set-up of water inside each of the compartments on the 2nd Deck. The result of this is that the mean equilibrium water level in the regular beam sea cases is higher than the equivalent calm water case. This is particularly noticeable for the two compartments on the port 2Centre-S15.
side, 2Aft-S11 and
It was found that a set up of similar magnitude also occurred at both port-side compartments (2Aft-S11 and 2Centre-S15) when the model was fixed at heel angles of 5 and 10 degrees. However, this set-up appeared to reduce at 5 degrees of heel and is not present at 10 degrees of heel for the wave probe located along the model centreline (2Fwd-S16) and the probe on the starboard side near the damage opening (2Centre-S12). This reduction in water level set-up at these two locations appeared to be approximately linear with increasing heel angle.
Further investigation is required to determine what effect wave frequency and/or wave height may have on these results.
The results for the fully constrained model presented here form one phase of several undertaken as part of the validation process for the non-linear time domain code, FREDYN. Macfarlane et al. (2010) presented results for the fully unconstrained model in calm water. Preliminary findings from both phases have provided encouraging
A-64 ©2012: The Royal Institution of Naval Architects
Water Level
(mm)
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