CAD/CAM SOLAS SLF 47 (SDS) Reg. 25-1
Probabilistic Damage Stability Harmonised proposal (HARDER)
Probabilistic Damage Stability
MSC.143(77)
MARPOL Reg. 12A
Reg. 19&23 Reg. 18(2) Reg. 23 Reg. 24 Reg. 25 Reg. 26
Reg. 27 Reg. 28
Stability Book Preparation Load Lines
a major milestone in this work. The NAPA ER tool brings together the functions for emergency response in one graphical user interface. Now used by both classification societies and ship operators, the ER tool has a proven track record in minimising loss and pollution by quickly evaluating rescue scenarios for a damaged vessel. During a critical situation such as a breach
Oil Fuel Protection
Clearance of Cargo Tanks
Segregated Ballast Tanks
Accidental Oil Outflow Performance
Damage Assumptions (hypothetical oil outflow)
Hypothetical Oil Outflow
Limitations of Size and Arrangement of Cargo Tanks Intact Stability
Subdivision and Damage Stability Ballast Water
Exchange Manager
or grounding, the ship’s staff can easily make mistakes when communicating vital information regarding the ship’s actual loading condition to the shore-based support. To counter this possibility for error, the actual loading condition of the ship can be exported by Onboard-NAPA and sent via email to the shore side NAPA ER installation. In this way there is little possibility for misunderstanding. By using the actual floating position and the pre- incident loading condition, the actual extent of damage can be determined.
Recoverability onboard The calculation of vulnerability and the simulation of flooding are closely related to the operational phase of the ship. One of the strengths of the NAPA system is the seamless integration throughout the design and life cycle. The same ship model can be moved from the designer’s computer to the network onboard the ship, where precise calculations can be made using the same design and production data. Scenarios can be tested onboard the vessel to
implementing many requirements even at the early design phase, thus reducing the risk of possible delays downstream.
Interface Links to other software formats are seen as an important part of the NAPA working philosophy. Downstream steel structure modelling, integration, outfitting design, and design for production can all be completed on the structure of the NAPA model developed at project inception. To support this, various links and interfaces have been developed over the years. These include links to Tribon, Autokon, NUPAS-CADMATIC, Autocad (DXF), Catia (VDA), LR RulesCalc, and interfaces such as DXF, VDAFS, STEP, and IGES. Using NAPA Steel’s automatic finite element
mesh generation, the model can be sent to an array of other applications to study a variety of specific characteristics, ranging from structural strength in shock, to hydro-acoustics.
Emergency response As naval platforms and especially the weapons system that they carry, become more complex and costly, the need for reliable decision support during damage scenario becomes even more evident. To respond to this need, Napa Ltd has developed
effective tools to support emergency response scenarios. NAPA ER (Emergency Response) was
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support the decision-making for normal seagoing stability tasks, or can be used to test recovery strategies for grounding, flooding, or structural damage. Often, time dependent factors such as tank filling rates play an important part in assessing the feasibility of a particular scenario. These are also incorporated into the user interface, and the ship’s office can monitor the predicted stability and strength characteristics throughout a proposed recovery scenario. With the developments in simulation, the rates of progressive flooding can also be predicted and retroactive actions can be determined. Most modern combatants have now moved
towards complex integrated platform management systems. In response to this, NAPA can now be installed on the ship’s network, and the ship’s stability and strength can be monitored from any workstation. In addition to this, NAPA can be installed as an imbedded API within the platform management system. In this way, the power of NAPA and the accuracy of the 3D model can be utilised within the existing infrastructure.
Route optimisation For many years NAPA has been used to predict the resistance and motion response of ships in waves. Now by using the same model in the ship life cycle it becomes possible to extend these hydrodynamic features to predict such route characteristics as speed, fuel consumption, and motion response. With the advent of optimisation using multi-
objective genetic algorithms, it became feasible to optimise the routing of a voyage to achieve minimum journey time or maximum fuel economy for a given arrival time. For several years now Napa Ltd has been working closely with clients to develop an easy to use tool that can be fitted onboard the ship. Recent results reported by Star Cruises after an extended test period onboard SuperStar Virgo have been very encouraging [5] and they have taken the decision to expand the installation to more ships.
By also using the optimisation constraints of
NAPA Power, the ship’s staff have an effective tool not only to maximise speed or minimise cost, but also to minimise accelerations due to weather. Strip theory is used to calculate the hull motions through the proposed route; if the ship’s motions exceed the constraints, alternative routes are proposed by the optimisation routine. Therefore, in the case of a damaged ship, the fastest route home can be quickly found, taking into account wind and tides, whilst at the same time minimising the environmental loading placed on the damaged ship’s structure.
Conclusion Optimising the performance of the ship through careful design and operation is the goal of both navies and commercial ship operators. Thanks to the continuous contribution and feedback of the NAPA user community around the world, the capability of the NAPA system has developed so that ever more complex problems can be solved at the initial design stage, thus improving the quality of the design, and reducing operational and commercial risks throughout the life cycle of the project. Several naval ship constructors have used
NAPA as a central component of their design process for many years [6]. In recent years, naval authorities and design agencies and operators have also recognised the advantages of using software that already has a successful track record in the design, certification, and operation of merchant ships. The requirements of this user community have led to many features specifically tailored to navy ships. The defence industry will continue to shape the development of the NAPA system, and coupled with the needs of the mercantile sector, more exciting new tools are planned that will support ever more capable and revolutionary designs over the coming years.
* EUR ING Christopher Ridgewell, CEng, MRINA, is a naval architect at Napa Ltd.
Footnotes
[1] BOULOUGOURIS, E K; PAPANIKOLAOU, A D (2004) ‘Optimisation of the Survivability of Naval Ships by Genetic Algorithms’. 3rd Int EuroConference on Computer Applications and Information Technologies in the Maritime Industries, COMPIT’04, Siguenza, Spain.
[2] KUUTTI, I; UPPALA, V ‘Practical Design Approach to Cost-Optimized Ship Structure’. ICCAS 2005.
[3] IMO ‘Assumptions for Cross-flooding in Draft Regulation II-1/7-2.4’. IMO document SLF 45/3/8.
[4] PETERSEN L ‘The Naval Ship Code – A New Safety Standard for Naval Vessels’. Naval Forces No V/2005 Vol XXVI.
[5] ‘Fuel Savings with Optimisation Software’. The Naval Architect, May 2006.
[6]
www.napa.fi > Products > NAPA > References.
WARSHIP TECHNOLOGY MAY 2007
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