Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010
10 15 20 25 30 35 40 45
0 5
measured
calculated, rough calculated, detailed
open door with a high sill (Figure. 5b). In the final phase of the flooding the water progressed from the pump and equipment rooms to the empty tank in the intact side (PS) of the ship through two open manholes (Figure. 5d). Both air pipes in the damaged tank were open and no notable air compression was observed in any of the flooded rooms. Thus all the rooms were modelled as fully vented in the simulation. The final calculated floating position is shown in Figure. 16.
The time histories for measured and calculated heel and trim
angles are presented 0 20 40 60 80 100 Time [s]
Figure 15: Airflow velocity in the air pipe for the side tank flooding
The measured and calculated flow velocities in the “damage hole” valve are presented in Figure. 14. The measurement did not succeed at small velocities, and consequently the flow seems to stop too early. However, the general correspondence with the simulation is good.
The measured air flow velocity in the centre of the air pipe is shown in Figure. 15. It is noteworthy that the maximum flow velocity is almost 40 m/s, even through the damage size is small and the maximum overpressure is only 2.0 kPa. Similarly to the water flow measurement, the flow seems to stop too early. This is caused by the unreliability of the applied pitot tube with small flow velocities. The presented simulation results are average velocities in the pipe cross-section, and thus they are not fully comparable with the measurement.
4.2 ONE-COMPARTMENT FLOODING
In this test the side tank with the damage hole was first flooded and then water proceeded to the equipment room through an
longitudinal bulkhead
0.5 1.0 1.5
−3.5 −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0
measured
calculated, rough calculated, detailed
open valve that was installed in the (Figure.
5a). The flooding then continued to the pump room through an progressive Figure 16: One-compartment flooding case
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
0 300 600 900 1200 Time [s] Figure 17: Heel angle for one-compartment flooding ©2010: The Royal Institution of Naval Architects 1500 1800 2100 2400 0 0 300 600 900 1200 Time [s] Figure 18: Trim angle for one-compartment flooding A-203 1500 120 140 160 180 in Figure. 17 and 18,
respectively. Contrary to the side tank flooding case, the rough estimations for the discharge coefficients result in too fast flooding. This is explained by the large pressure losses in the valve between the side tank and the equipment room. The dedicated hydraulic tests of the valve in the flume at Aalto University confirmed that the effective discharge coefficient is much smaller than the rough estimation (Cd = 0.60) when the flow discharges to air with a small pressure head.
The trim angle is slightly over-estimated in the simulations, especially in the early stages. This results from the observed fact that water first accumulated between the stiffeners. This was not taken into account in the numerical model. Thus
in the simulations water
immediately accumulated to the forward part of the room due to the bow trim.
The sudden increase of the heel angle at t ≈ 900 s is under-estimated by the simulation. At this time the flooding of the pump room starts. Therefore, the likely explanation for the
difference is that water is
accumulated between the structures on the damaged side of the pump room.
measured
calculated, rough calculated, detailed
1800 2100 2400
Heel [deg]
Air velocity DN65 [m/s]
Trim [deg]
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