Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010
4. VALIDATION OF THE SIMULATION METHOD
4.1 FLOODING OF A SIDE TANK
In this test the ventilation level of the flooded side tank was restricted. The diameter of the air pipe is 65 mm and the pipe length is approximately 2.5 m, including several bends (Figure. 10). The larger air pipe was closed in this test. Thus the air pipe size is less than 7 % of the damage hole area. This is much smaller than required in the IMO Resolution MSC.245(83) [12] for assumption of full ventilation in a cross-flooding calculation. The discharge coefficient for the airflow in the pipe was estimated by using the formulae in the Appendix of the IMO Resolution MSC.245(83), resulting in Cd,air = 0.62.
The measured and calculated heeling angles are presented in Figure. 11 Air overpressure and water level in the flooded side tank are presented in Figure. 12 and 13, respectively. There was no notable change in the trim angle. The simulation with the rough estimations results in too slow flooding. Also the peak of the air pressure is under-estimated.
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
Figure 10: Flooded side tank with the small air pipe
With more realistic input data the correspondence to the measurements is much better. However, especially the air overpressure in the tank is equalized slightly later than measured.
In comparison of measured and calculated water levels, some difference can be noticed in the start of the flooding. This is explained by the fact that the stiffeners and brackets in the bottom of the tank (Figure. 4a) delayed the progress of floodwater inside the tank and resulted in more rapid change of the water level at the sensor location.
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
0 20 40 60 80 100 Time [s] Figure 11: Heel angle for side tank flooding
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25
0 0 20 40 60 80 100 Time [s] Figure 13: Air overpressure for side tank flooding 120 measured
calculated, rough calculated, detailed
120 140 160 180 0 0 20 40 60 80 100 Time [s] Figure 12: Water level in the flooded side tank
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
140 160 180 0 0 20 40 60 80 100 Time [s]
Figure 14: Flow velocity in the damage opening for the side tank flooding
A-202 ©2010: The Royal Institution of Naval Architects 120 measured
calculated, rough calculated, detailed
120
measured
calculated, rough calculated, detailed
140 160 180
140
160
180
Air overpressure [kPa]
Heel [deg]
Water velocity V1 [m/s]
Water level A1 [m]
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