Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010 TECHNICAL NOTE
THE TRANSIENT EFFECTS OF FLOOD WATER ON A WARSHIP IN CALM WATER IMMEDIATELY FOLLOWING DAMAGE
G J Macfarlane and M R Renilson, Australian Maritime College, University of Tasmania, Australia T Turner, Defence Science & Technology Organisation, Australia (DOI No: 10.3940/rina.2010.a4.197tn)
SUMMARY
The safety of a ship which is damaged below the waterline will depend on the way water floods into the internal compartments. The water will cause the ship to take on an angle of heel and trim which will further affect the flooding into the compartments. The ship’s equilibrium position in calm water can be predicted using hydrostatic theory, however at present it is difficult to predict the transient behaviour between the initial upright position of the ship and its final equilibrium. In some cases, the transient motion may cause a capsize prior to a possible equilibrium position being reached.
This paper describes an investigation of this phenomenon using a model of a warship with simplified, typical internal geometry. With the model initially stationary, a rapid damage event was generated, and the global motions measured, along with the water levels in some of the internal compartments, as functions of time. Immediately after the damage occurred the model rolled to starboard (towards the damage). It then rolled to port (away from the damage) before eventually returning to starboard and settling at its equilibrium value. In all the tests conducted the equilibrium heel angle was less than that reached during the initial roll to starboard. This implies that the roll damping, and the way in which the water floods into the model immediately following the damage, could both have a very important influence on the likelihood of survival.
1. INTRODUCTION
When a ship suffers damage below the waterline water will flood into the internal compartments that have become open to the sea. This will result in it taking on an angle of heel and trim.
result in capsizing or sinking of the ship (Turner et al. 2010).
Although the equilibrium position in calm water can be calculated using traditional hydrostatic theory, the transient behaviour which occurs between the initial position of the ship and its final equilibrium may cause a capsize where static theory suggests that the vessel would survive. In addition, the dynamic effects during the transient phase may allow additional water to enter through the
hull opening, equilibrium position to that obtained from statics alone.
In order to investigate this behaviour for a warship with a complex internal geometry, model experiments were conducted in the Model Test Basin at the Australian Maritime College (AMC) on a model of a generic destroyer hull form (Macfarlane and Renilson, 2010, Ypma and Turner, 2010). The tests were sponsored by the Cooperative Research Navies group (CRN) to assist in validating the accuracy of the flooding model used in a non-linear time domain code, FREDYN.
2. MODEL DETAILS
A 3.268 metre long model (LOA) of a generic destroyer was constructed and fitted with a removable perspex
©2010: The Royal Institution of Naval Architects
• simplified tanks • simplified 2nd Deck • simplified 1st Deck
The layouts of the compartments for each deck level are provided in Figure 5(a, b and c). The designation for each compartment is given in these figures. All hatches and doors shown in these
module containing an arrangement of the internal compartments, which, although not as intricate as that of a full scale ship, has the necessary complexity to be used to investigate the phenomena associated with progressive flooding. The scale factor was 1:45.
In extreme cases it may
The principal particulars of the model are provided in Table 1. The profile and body plan of the model are shown in Figures 1 and 2, respectively. A photograph of the model is shown in Figure 3. The model was fitted with bilge keels and fixed stabiliser fins as shown in Figure 4.
resulting in a different
The model was fitted with four transverse bulkheads with the two end bulkheads made watertight to contain the flooding. The following tanks and deck levels were also modelled:
figures remained open
throughout the duration of the test program. Cross sections at the locations AA, BB and CC indicated in this figure are provided in Figure 6(a, b and c). The approximate locations of the four transverse bulkheads (B1, B2, B3 and B4) are indicated on the profile of the model, shown in Figure 1. Further details about the
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