Integrated Flooding Control and Standard for Stability and Crises Management FLOODSTAND-deliverable : IMPACT OF SHIP DYNAMICS IN FLOODING SIMULATION

The roll motions of a modern passenger cruise vessel are studied in two different damage cases. NAPA Flooding simulation tool is applied for the study of the floodwater progression in a calm water condition. The impact of ship dynamics are studied in damage case by applying the floodwater to a seakeeping and manoeuvring code LAIDYN. The lumped mass concept for floodwater modelling is adopted and described. The impact of the irregular waves to the roll motion is studied. With the applied method the transient and the wave induced ship motions are seen to occur in average around the quasi-static predicted heel angle. Acknowledgements The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 218532. The financial support is gratefully appreciated. The contribution of Pekka Ruponen and Napa Ltd. is greatly valued. Disclaimer Neither the European Commission nor any person acting on behalf of the FLOODSTAND Consortium is responsible for the use, which might be made of the following information. The views expressed in this report are those of the authors and do not necessarily reflect those of the European Commission and other members of the FLOODSTAND Consortium. Copyright © 2011 FP7 FLOODSTAND project consortium Reproduction is authorised provided the source is acknowledged FLOODSTAND Impact of Ship Dynamics 3.10. 2011 FP7-RTD-218532 in Flooding Simulation D3.2 Final Version 1.1 1 CONTENTS Page CONTENTS . 1 1 Executive Summary . 2 2 Introduction . 3 2.1 Background . 3 2.2 Task definition . 3 2.3 Previous works . 3 3 Simulation Method . 4 3.1 Flooding simulation . 4 3.2 Simulation of ship motions . 4 4 Case study . 6 4.1 Studied ship . 6 4.2 Damage case 1. 7 4.3 Damage case 2. 7 5 RESULTS. 9 5.1 Simulated cases . 9 5.2 Intact ship in waves . 10 5.2.1 Intact ship, sea state Hs = 2.5 m . 10 5.2.2 Intact ship, wave case Hs = 4.0 m . 11 5.2.3 Intact ship, wave case Hs = 6.5 m . 12 5.3 Damage case 1. 13 5.3.1 Damage case 1, sea state calm . 13 5.3.2 Damage case 1, wave case Hs = 2.5 m . 15 5.3. 3 Damage case 1, sea state Hs = 4.0 m . 16 5.3. 4 Damage case 1, sea state Hs = 6.5 m . 17 5.4 Damage case 2. Results . 18 5.4.1 Damage case 2, sea state calm . 18 5.4.2 Damage case 2, sea state Hs = 2.5 m . 20 5.4.3 Damage case 2, sea state Hs = 4.0 m . 21 5.4. 4 Damage case 2, sea state Hs = 6.5 m . 22 6 Conclusions . 23 7 References . 24 FLOODSTAND Impact of Ship Dynamics 3.10. 2011 FP7-RTD-218532 in Flooding Simulation D3.2 Final Version 1.1 2 1 EXECUTIVE SUMMARY The objective of the WP3 Task 3.2 was to study the impact of the sea state to the reliability of the system of flood sensors and simulation tools for predicting of ship motions. In order to account for the sea state in the flooding simulation a dynamic model of sea keeping simulations must be integrated with the flooding simulations. The LAIDYN code developed at the Aalto University for the sea keeping and manoeuvring simulations and the NAPA flooding simulation codes are applied to study the damaged ship motions and flooding at the calm sea and wave conditions. Case studies for a damaged passenger cruise ship design, a concept ship of 63.000 GT with length of 238 meters, were performed. Two different damage scenarios were simulated in irregular sea conditions. First damage scenario is a damage of two rooms on the side of the ship. In addition third room is flooded through a cross flooding duct. The breach size allows fast and asymmetric flooding which results in a pronounced transient roll motion. The second damage case is a raking damage over three compartments. Breach size is smaller and flooding is slower than in the first damage scenario. Ship design, in this damage case, was intentionally changed to have poorer transversal damage stability. In the second damage case the transient motions are not that important but the damage and divisions of the flooded rooms result in larger heel angle. The progression of the flooding was simulated in the calm water conditions using quasi-static simulation method. The roll motions were simulated by the dynamic simulation method, which could account for the transient ship motions due to flooding and the wave induced motions. Floodwater mass from the quasi-static simulation is applied to the dynamic simulation code. Dynamic ship motions both in the damage and intact case were then simulated in the presence of irregular beam seas. Exactly the same sets of irregular waves were applied to the intact and damaged cases. Comparison of the roll motion between the intact and damaged cases in the irregular waves shows that the damaged ship rolls largely around the heel angle predicted by the quasi-static simulation in the calm water. In the applied model the floodwater volumes are not affected by the ship motions and the floodwater free surface remains horizontal. Thus some important phenomena of the floodwater behaviour are omitted for the sake of simplicity. The dynamic behaviour of the floodwater depends on many factors like detailed geometry of the flooded room and its permeability. More detailed modelling requires specific information on the obstacles in the rooms which is often not even available. If the flooding is to be predicted with some sensor system the transient and wave induced motions should be filtered out from the sensor output. Simulations of ship motions with the described model of given amounts of floodwater clearly show that the average roll angle is of same magnitude than the quasi-static result in calm water. This gives a possibility to predict the overall flooding by using moving average over a time period longer than the ship natural roll period to smoothen the output. The dynamic simulation predicted roll angle processed by moving average, results in a quite close accordance with the quasi-static heel angle. Yet again the use of the floodwater volumes from the quasi-static simulation is a strong limitation of the applied dynamic simulation model and does not allow a real interaction of the ship and floodwater motions. The importance of this limitation should be studied further on. FLOODSTAND Impact of Ship Dynamics 3.10. 2011 FP7-RTD-218532 in Flooding Simulation D3.2 Final Version 1.1 3 2 INTRODUCTION 2.1 Background The safety of large number of passengers that a modern passenger cruise vessel can accommodate is of utmost importance. In case of an accident resulting in the loss of watertight integrity of the ship and consequent flooding, the available options to ensure the safety of the passengers are the transportation of the ship to the port or evacuation. The feasibility of these options depends greatly on the residual stability of the ship after the damage. Onboard tools for fast assessment of