Validation of a Software Tool (DROPSIM) to Predict the ‘Drop and Getaway’ Behaviour of a Lifeboat

The purpose of a free fall lifeboat is to evacuate people from platforms in case of emergency, and when other, normal means of evacuation, are not possible. For instance, when the weather is too rough, and evacuation cannot be performed by helicopters, the lifeboats are the last way of escape. It is thus essential to be able to properly assess the operability of a lifeboat and the safety of its occupants upon evacuation.Over the past four years, methods to quantify the operability limits of a lifeboat were analysed in a research project carried out for Statoil. As part of this project, a prototype software (denominated DROPSIM) was developed to predict the ‘drop and sailaway behaviour’ of a lifeboat. DROPSIM is a simplified method based on strip theory, with the objective to obtain predictions that are consistent with the relevant statistical behaviour of the lifeboat, and for the same target level of probability.Particularly because DROPSIM is a simplified tool, it is vital to verify that the software is adequate for simulating thousands of random lifeboat drops, yielding robust statistical predictions with sufficient accuracy. In order to show the performance of the simulation tool, an extensive validation procedure was established, based on a large amount of model test and data from other simulation tools. The following topics were considered in the validation:A. Verification: basic checks, e.g. related to buoyancy without comparison to model testsB. Consistency of simulated and measured response for basic test cases, including free-falling wedge tests and a variety of impact tests with a bullet shaped modelC. Prediction of the sailaway behaviour of a lifeboat in comparison to model testsD. Comparison with integrated drop and sailaway model tests in normal and off-design (extreme) conditions in calm water and in waves.In this paper the results of the validation of DROPSIM are presented and discussed. Another dedicated paper gives insight into the mathematical model of DROPSIM ([1]).Copyright © 2015 by ASME