Napa Ltd.

Helsinki, Finland

Napa Ltd.

Helsinki, Finland
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Kuutti I.,Napa Ltd. | Mizutani N.,Napa Japan Ltd. | Kim H.S.,Napa Korea Ltd.
RINA, Royal Institution of Naval Architects - International Conference on Computer Applications in Shipbuilding 2011, Papers | Year: 2011

3D design software has been available for decades and has been effectively applied in ship building production design. Despite this, but 2D drafting is still the method most commonly used for design and sharing information during the early design stages. A shared 3D product model has considerable benefits for collaborative working and efficiently integrates engineering with a common source of design information. The challenge so far has been that creating the 3D model takes too long to match the timeline during the early design stage. For this reason, the traditional tools developed mainly for detail design are not applicable during the early design stages. Dedicated 3D software developed specifically for the early design stages can provide designers with tools that are fast enough, but this approach then creates the need for integration with other design disciplines and tools. This paper describes some example cases from the real design environment where 3D models have been applied in practice, and presents one technical solution integrating the design disciplines, design stages and tools applied in ship design. The solution is briefly reviewed and some example results are presented. ©2011: The Royal Institution of Naval Architects.

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: SST-2007-4.1-01;SST-2007-4.1-03 | Award Amount: 4.33M | Year: 2009

The size of new passenger ships is continuously increasing. Bigger size offers bigger opportunities and economics of scale, but when a bigger ship accommodates more passengers there may be a higher risk, if evacuation is needed. Thus, new approaches have to be used and further developed in order to have the flooding under control if the watertight integrity of the ship is lost. In the worst case, all flooding accidents may lead to the capsizing or sinking of the ship within a highly variable time frame. The need to ensure safe return to port or at least sufficient time for abandonment, will form major challenge in ship design. However, the assessment of the available time and the evacuation decision are not easy tasks. This process is complicated and there is a notable lack of data. Thus, guidelines and methods to tackle these problems must be developed. New tools are required in order to increase the designers and operators possibilities to reliably evaluate the ships capability to survive in flooding accidents. This project sets to derive most of the missing data for validation of time-domain numerical tools for assessment of ship survivability and to develop a standard for a comprehensive measure of damaged ship stability, as a means of addressing systematically, rationally and effectively the risk of flooding. Unlike any current regulations the envisaged standard will reflect the stochastic nature of the damaged ship stability in waves. It will be based on first-principles modeling and thus it will reflect the nature of foundering as a process comprising loss of either (or both), flotation and stability, but also and more importantly ultimate loss of human life. Since risk-based, the standard will form a basis for decision support. It is expected that by explicit disclosure of the risks associated with ship flooding and thus addressed from early design to operation, the safety level can be raised substantially from levels of current legislation.

Bulian G.,University of Trieste | Lindroth D.,NAPA Ltd | Ruponen P.,NAPA Ltd | Zaraphonitis G.,National Technical University of Athens
Ocean Engineering | Year: 2016

This paper presents the results of ongoing research efforts aimed at the theoretical development and practical implementation of a probabilistic framework for regulatory assessment of ship survivability following grounding accidents, with particular attention to passenger vessels. In the envisioned framework, the probabilities of flooding of a compartment, or a group of compartments, i.e. the so-called "p-factors", are determined using a flexible and easily updatable direct non-zonal approach. The assessment of the conditional ship survivability, on the other hand, is based on the SOLAS "s-factor". The general framework is described, together with implementation details in the specific case of bottom grounding. Testing results, carried out using a specifically developed software tool, are also reported. © 2016 Elsevier Ltd. All rights reserved.

Manderbacka T.,Aalto University | Manderbacka T.,NAPA Ltd | Ruponen P.,NAPA Ltd
Ocean Engineering | Year: 2016

Dynamics of an abrupt flooding case are studied by comparing fully dynamic and quasi-static flooding simulation methods. Transient asymmetric flooding is traditionally modelled by dividing the compartment into smaller parts with bulkheads representing different obstructions in the flooded compartment. The implications of this assumption are studied by varying the size of the opening on the dividing bulkhead. The importance of the inflooding jet to the response is shown. The jet i.e. the inflooding momentum flux is modelled as force acting on the lumped mass. When the flooded compartment does not have significant obstructions it is important to account for the inflooding momentum flux. © 2016 Elsevier Ltd. All rights reserved.

Manderbacka T.,Aalto University | Ruponen P.,Napa Ltd | Kulovesi J.,Aalto University | Matusiak J.,Aalto University
Journal of Fluids and Structures | Year: 2015

Coupling of the flooded water and ship motions was studied experimentally. Roll decay tests for one flooded compartment and transient abrupt flooding tests were performed for the box shaped barge model. The tests were conducted to obtain information on the flooding process for the development of numerical tools and to provide validation data. Quantitative values on the effect of flooded water on the roll damping were obtained. Flooded water behaves in a different manner in undivided and divided compartments. Flooded water in divided compartment increases roll damping significantly. In undivided compartment roll damping was high at low amount of flooded water. For higher amounts damping was of the same order as for the intact model. Initial flooding is a complex process where the ship and flooded water motions are coupled. Propagation of the flooding water inside the compartment, at a dam-break type abrupt flooding, was studied by tracking the surface of the flooded water. An image processing algorithm was used to obtain the tracked surface. Flooded water volume and its center of gravity were estimated from the tracked surface. Different internal layouts of the flooded compartment can lead to a totally different roll response. The inflooding jet plays an important role in the response in case of the undivided compartment. While, for a divided compartment, asymmetric flooding due to the obstructions causes high heel angle on the damage side. © 2015 Elsevier Ltd.

Manderbacka T.,Aalto University | Mikkola T.,Aalto University | Ruponen P.,Napa Ltd | Matusiak J.,Aalto University
Journal of Fluids and Structures | Year: 2015

Numerical non-linear time domain simulation method for damaged ship motions is presented. Floodwater motion modelling is based on the lumped mass method with a moving free surface. The ship and floodwater motions are fully coupled. The variation of the floodwater mass is accounted for. A model to account for the flooding ingress transporting the momentum is presented. The experiments of abrupt flooding have shown that the ship may experience the first large roll towards the undamaged side, especially when a large undivided compartment is flooded. The presented time domain model is validated against the experimental data on the roll damping of the flooded ship and transient flooding. Two different initial stability conditions and two different compartment layouts are studied. Viscous dissipation of the floodwater motions is modelled with an equivalent friction coefficient. The impact of the viscous damping is studied. Transient flooding tests show that the inflow momentum has to be accounted for when the undivided compartment is flooded. The simulation model is capable of capturing the impact of the inflooding jet and the first roll on the opposite side of the damage is reproduced. © 2015 Elsevier Ltd.

Ruponen P.,Napa Ltd | Kurvinen P.,Aalto University | Saisto I.,VTT Technical Research Center of Finland | Harras J.,Finnish Naval Research Institute
Ocean Engineering | Year: 2013

Air compression inside a flooded tank of a damaged ship can significantly delay the flooding process if the ventilation is restricted. This is a notable issue that needs to be considered for example in the design of cross-flooding devices. The problem is studied through systematic full-scale tests with a decommissioned ship, where the ventilation level of a flooded tank could be altered. Comparative time-domain flooding simulations have been performed by using Bernoulli's equation for compressible fluid for calculation of the air flows. The analysed measurements are used to validate the applied numerical method and relevant conclusions are drawn. © 2012 Elsevier Ltd.

Ruponen P.,Napa Ltd.
Ocean Engineering | Year: 2014

Time accurate simulation of progressive flooding inside a ship often requires a short time step. However, after the initial phases, as the flooding progresses to undamaged compartments, the flow rates decrease and much longer time step could be used. Yet the collapsing of non-watertight structures may cause additional phases of fast flooding, where a shorter time step is required. In this paper the use of an adaptive time step in flooding simulation is discussed, and a new approach to this problem is presented. The time step is automatically adjusted during the simulation on the basis of the maximum absolute velocity of the free surface levels in the flooded compartments. The method is tested with small case studies, presenting typical flooding conditions in passenger ships. © 2014 Elsevier Ltd.

Ruponen P.,Napa Ltd
Fluid Mechanics and its Applications | Year: 2011

The principle idea of using pressure-correction method for time-domain flooding simulation is presented. Special attention is paid on the handling of large openings and relevant modifications to the equations. Practical examples of application are also discussed. First, progressive flooding in a complex system of rooms and openings of a passenger ship is presented. The study concentrates on the effect of input parameters for non-watertight structures. The second example demonstrates cross-flooding calculation with the air compressibility taken into account. © Springer Science+Business Media B.V. 2011.

Polmi M.,Intergraph | Hulkkonen T.,Napa Ltd.
RINA, Royal Institution of Naval Architects - International Conference on Computer Applications in Shipbuilding 2015, ICCAS 2015 - Papers | Year: 2015

Due to an increased focus on safety and swvivability, major projects utilize higher and higher fidelity 3D models developed in the early design stages as the basis for first pruiciples-based analyses and simulations. Many of these solutions offer 3D modeling capabilities that support the rapid development of models with the necessary goometiy and properties needed for the analyses. Because of the increased sophistication of these models and analysis tools, the up- front engineering costs and lead-times have increased. While the 3D modeling features of these solutions are getting more and more powerful, they are limited and not on par with state-of-the-art, integrated, lifecycle 3D modeling tools on the market today. Prqject costs and schedules can benefit from a capability to re-use this 3D model data as the design moves from the early stages where the focus is on the engineering design to the downstream stages where the focus is on construction and production. The authors have cooperated in the development of an interface between two market-leading solutions with strengths at the different ends of the engineering spectrum-Napa concentrating on the early design phases like stability. thip performance, plan approval, structural FEM analysis and Class Rule Checks and Intergraph's Smazi3D that provides an integrated, concurrent enterprise solution strong in detail and production design for hull, structure, and outfitting. The authors will present the case that used together-these tools enable a customer to work with 'best of breed" solutions in every design phase that offer a strong integration with modern IT-technology and will provide an effective means of leveraging their investment in 3D modeling and yielding productivity and cost savings for the project This development project has successfully integrated these two Systems and guarantees the continuous drmgn flow of information for the customer without duplicated work. In addition to highlighting key features and functions, they will discuss the benefits of this approach as it relates to several targeted projects in the marine industry. © 2015: The Royal Institute of Naval Architects.

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