# Calculation Method to Include Water on Deck Effects

• Nicolas F. A. J. Carette
• Frans van Walree
Chapter
Part of the Fluid Mechanics and Its Applications book series (FMIA, volume 119)

## Abstract

Green water is an important issue regarding ships stability as it may dramatically change the loading of the ship compared to its dry deck condition. Until now, computational methods capturing this event are very time consuming as they often try to capture the complete dynamics of the flow over the vessel’s structure and deck using CFD. Such methods are not practical when dealing with numerous lengthy time domain simulations for long term stability assessments. MARIN has developed a fast method to be implemented in its 6 DOF time domain program FREDYN. This method has as objectives to be as fast as possible, even real time if achievable, but at the same time take into account correctly the mass of water flooding on the deck during green water events. The method is based on pre-computing the steady forward speed wave pattern and diffracted and radiated waves. The steady wave is computed for a series of sailing conditions using the in-house 3D linear panel code DAWSON. The diffracted and radiated waves are pre-computed using in-house 2D strip theory potential code SHIPMO for a series of frequencies and sailing conditions. A ship generated wave is then computed at each time step during the simulation using the current position and motions of the ship. This improves the computation of a realistic wave elevation consisting of the incident, steady, diffracted and radiated waves along the hull of the ship. This wave profile is then used to feed our flooding module which computes flows in tanks, compartments and through openings. This flooding model is based on a quasi-static Bernoulli formulation and empirical discharge coefficients. It is used to compute the flow over the bulwarks and through the freeing ports to the deck.

## Keywords

Time domain Green water Capsize Calculations FREDYN

## Notations

z

Incoming wave [m]

$$\tilde{\zeta }$$

Diffracted wave [m]

$$\tilde{\zeta }$$

$$\omega$$

Wave frequency [s−1]

$$\kappa$$

Wave number [–]

n

Index for frequency [–]

i

Index for section [–]

$$\varepsilon$$

Incoming wave phase [–]

$$\tilde{\varepsilon }$$

Diffraction wave phase [–]

$$\phi_{rad}$$

## Notes

### Acknowledgements

This research is performed for the Cooperative Research Navies. The permission of the CRN to publish the results is gratefully acknowledged.

## References

1. de Kat J.O. and Paulling J.R., ‘Prediction of extreme motions and capsizing of ships and offshore vehicles’, Proc. of the 20th OMAE Conference, Rio de Janeiro, June 2001.Google Scholar
2. Van Walree F., ‘Seakeeping deck Edge Immersion Model Tests’, MARIN Report 22810-1-CPS, 2010.Google Scholar

© Springer Nature Switzerland AG 2019

## Authors and Affiliations

• Nicolas F. A. J. Carette
• 1
• Frans van Walree
• 1
1. 1.MARIN-Maritime Research Institute NetherlandsWageningenThe Netherlands