Trans RINA, Vol 154, Part A2, Intl J Maritime Eng, Apr-Jun 2012
constructed out of perspex. The principal particulars of the model are provided in Table 1.
Length overall Draught
Length between perpendiculars 2961 mm Beam
3268 mm 412
118 Table 1 Model principal particulars
The layout of compartments for each of the three deck levels are shown in Figure 1(a, b and c) and cross sections at locations AA, BB and CC are provided in Figure 2(a, b and c). Detailed information about the model, such as the compartment dimensions and volumes; the names, locations and sizes of each of the hatch openings and doorways between the internal compartments; locations of each sensor; and details of the damage to the provided in
hull, Macfarlane
bulkheads and decks, are and Renilson (2010) and
Macfarlane and Hutchison (2010).
A very rapid damage opening scenario was simulated by rupturing the taut membrane by either sharp blades or hot wires that were operated by a remote switch. The hot wires were used in the later tests as this proved to be a more reliable technique. Rupturing the membrane in this way resulted in the loss of the latex patch within 1/25th second (one video frame), leading to a very rapid damage event. A wave probe was located on the 2nd Deck immediately inboard of the damaged membrane to provide a reliable time datum with the acquired data for when the damage occurred.
3. EXPERIMENTAL SET UP
For all experiments covered in this paper the model was at zero forward speed. The test rig was set up such that the model was fully constrained in all six degrees of freedom (surge, sway, yaw, heave, pitch and roll). In all cases the model was located approximately in the centre of the experiment basin to avoid any interaction with the test basin walls.
Two pairs of draught gauges were fitted to the model to set the required draught.
These were checked
periodically to ensure that small changes in water level in the basin did not influence the draught of the constrained model (which was not free to heave if the water level changed).
A total of seven wave probes were included to measure the water levels in the following compartments: 0Fwd- S06; 2Aft-S11; 2Centre-S12; 2Centre-S15; 2Fwd-S16; 1Aft-S17 and 1Centre-S23 (the location of these wave probes is indicated by the symbol ‘WP’ in Figure 1). In addition, pressure transducers were fitted into tank
A-54
Displacement 68.63 kg LCG (forward of AP)
mm mm
1418 mm
0Fwd-S06 and compartment 2Centre-S12 (indicated by ‘PP’ in Figure 1). All wave probes were regularly calibrated and double-checked by applying a reference datum (known water depth) following the completion of most test runs.
The air pressures within tank 0Fwd-S06 and
compartment 2Centre-S12 were measured using Endevco pressure transducers (model number 8510B-2) having a range of 13.8 kPa (2.0 psi) linked to an Endevco Model 136 DC amplifier.
On completion of data acquisition the model was removed from the basin, the water was emptied from all tanks and a new latex membrane fitted prior to setting up for the next run.
Once the model was prepared and
located, the basin was allowed to return to a calm state before the next run was begun.
The following levels of uncertainty were estimated:
Model dimensions = breadth and draught ±1.0 mm and for length ±1.5 mm
Model displacement = ±100 grams Water surface elevation = ±2.0 mm
4. RESULTS AND DISCUSSION
4.1 COMPARTMENT WATER LEVELS AND AIR PRESSURES
Figure 3 shows the water elevations at each wave probe within the four selected compartments as functions of time.
In all cases these elevations represent the raw
wetted lengths of each sensor, with a zero reading corresponding with no water at the base of the wave probe. Note that the damage initiation occurs for all time series plots presented in this paper occurs at time t = 0 seconds.
As can be seen, the water levels at each of the three probes on the 2nd Deck (2Centre-S12, 2Centre-S15 and 2Aft-S11) have all reached equilibrium within about 12s after damage initiation. The probe in compartment 2Centre-S12 very rapidly reaches an equilibrium value, which was expected given that this is the compartment where the damage opening in the hull is located and as such there are no restrictions to impede the incoming flow of water.
The relatively slower rise in water level at the probes in the two port-side compartments, 2Aft-S11 and 2Centre- S15, provide an indication as to the additional time required for the water to pass through the open doorways and neighbouring compartments. The probe in the tank 0Fwd-S06 indicates that it took considerably longer (approximately 38s) for this lower tank to fill with water as the water flowed into this compartment via a smaller hatch opening rather than a larger doorway opening.
©2012: The Royal Institution of Naval Architects
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