10 January 2009

Progressive Flooding of a Damaged Passenger Ship - Pekka Ruponen

Progressive flooding inside a damaged passenger ship was studied with time-domain simulations. A novel computational method was developed for this purpose. Typically, the layout of the watertight compartments in this ship type contains numerous openings and rooms with complex geometry. In the voids the flooding can also result in air compression since the ventilation of these rooms is restricted due to the relatively small air pipes. These factors are significant for time-accurate simulation of progressive flooding.

The developed method is based on pressure correction technique. This iterative and implicit approach is suitable for time-accurate simulations. The progress of the floodwater is considered on the basis of the hydrostatic pressure (i.e. the water height) in the flooded rooms. The widely used hydraulic model, based on Bernoulli's equation, is used for the calculation of the flow velocities. The pressure-correction equation is formed from the conservation of mass and the linearization of Bernoulli's equation. The ship is considered as a staggered and unstructured grid, where the hydrostatic and air pressures are solved in the centers of the rooms and the flow velocities in the openings. Also the counter pressure due to air compression and the resulting airflows can be solved. All water levels are considered to be flat and parallel to the sea level. The main emphasis of the study is on the calculation of the flooding inside the damaged ship, and therefore, a simple quasi-stationary approach is used for the evaluation of the ship motions. The standard procedures of the NAPA software are utilised for this. In addition, it is assumed that the sea is calm.

The developed simulation method has been extensively validated by comparing simulation results with the measurement data from model tests for progressive flooding and air compression in a damaged box-shaped barge. The results of the validation show very good correspondence between the simulations and the measurements.

The applicability of the developed simulation method has been tested by performing simulations of cross-flooding and extensive progressive flooding for a 40 000 GT passenger ship design. The latter test case involves flooding through leaking and collapsed structures and slow down-flooding in a large and complex system of rooms and openings.

Keywords: progressive flooding, damage stability, pressure correction, passenger ship

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Mechanical Engineering for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 16th of November, 2007, at 12 noon.

Dissertation in PDF format (ISBN 978-951-22-9013-0) [4106 KB]

credit to : http://lib.tkk.fi/Diss/2007/isbn9789512290130/

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