GL to Holds International Ship Stability Workshop

Monday, September 10, 2007
More than 70 experts from the international maritime industry met at Germanischer Lloyd headquarters to discuss the current status of the development and research in ship stability. The two day workshop dealt with the probabilistic assessment of intact stability, showed trends in progressive flooding prediction, presented new cognitions of investigations on severe stability incidents like the MV Estonia and informed about the simulation of parametric rolling. Surf-riding, broaching and capsizing in following/quartering seas, numerical prediction of intact stability as well as probabilistic approach to damage stability and survivability assessment plus intact capsize investigations rounded off the program of 28 presentations.

Under the topic "goal based stability standards" Lech Kobyliński, Foundation for Safety of Navigation and Environment Protection, gave a speech about this IMO-concept. Kobyliński said it is time to consider a holistic and risk based approach to stability standards as an alternative to the existing prescriptive criteria used in daily work. This should be done in order to enhance safety and not to hinder the development of novel ship types. He pointed out that the risk of capsizing could be minimized by more detailed considerations of the procedure and special identification systems of hazards as well as a methodology of risk assessment.

"Benchmark study of numerical codes for the prediction of time to flood of ships: Phase I" was the title of a presentation held by Frans van Walree, Maritime Research Institute Netherlands (MARIN), and Apostolos Papanikolaou, National Technical University of Athens (NTUA). The two experts presented a summary of the progress of an International Towing Tank Conference (ITTC) benchmark study on numerical codes for the prediction of time-to-flood of damaged passenger ships. For this study simulation data for the flooding of a vessel has been provided by developers of several numerical codes and compared with relevant model experimental data. The steady state flooding condition is reasonably well predicted by the codes. According to the speakers, the calculation of the flooding rates and transient phenomena is less satisfactory and urges on increased research effort in the future.

In a further presentation first results of the on-going investigation of the MV Estonia case were shown by Petri Valanto, Hamburg Ship Model Basin HSVA. Since March 2006 a consortium consisting of the HSVA, the Technical University of Hamburg-Harburg (TUHH) and TraffGo HT, is investigating the accident for the Swedish Governmental Agency for Innovation Systems (VINNOVA). The results mainly base on the motion simulation of the damaged ship in seaway carried out in the HSVA, including the simulation of the water sloshing on the vehicle deck. Relating to the studies and results, the participants of the workshop were able to get an idea of the early phases of the accident. Claudio A. Rodríguez, Department of Naval Architecture and Ocean Engineering, LabOceano/COPPE, Federal University of Rio de Janeiro informed in his speech about the "Validation of a Container Ship Model for Parametric Rolling". The aim of the presented study: to formulate a nonlinear, coupled model of a container ship during parametric roll resonance, and to validate the model using experimental data. The model agreed with the experimental and numerical results. Dr Ould M. El Moctar, Head of Department Fluid Dynamics at Germanischer Lloyd, held a presentation about the "Prediction of Extreme Ship Responses Using Potential Flow and RANSE Codes". He unveiled numerical procedures to simulate ship sea keeping responses involving extreme motions and loads for different ship types. For statistic and probabilistic long-term analysis of a ship's operation, potential-flow codes are needed to define representative environmental conditions. El Moctar made reference to the Reynolds-averaged Navier-Stokes equation (RANSE) which can offer superior simulation capability for extreme ship motions like capsizing, slamming and green water on deck.

The 10th International Ship Stability Workshop will take place in Daejeon, Korea in March 2008.

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