Experimental and numerical analysis of a damaged ship ...

1Centre for Autonomous Marine Operations and Systems - NTNU AMOSwww.ntnu.edu/amos

Experimental and numerical analysis of a damaged ship section in waves

Mohd Atif SiddiquiMain Supervisor: Prof Marilena GrecoCo- Supervisors: Prof Odd M. Faltinsen & Dr Giuseppina Colicchio


Outline

• Motivation

• Flooding phenomenon for damaged ships

• Experiments

• Selected experimental results– Forced heave motion

– Regular wave tests

• Numerical method– Forced heave motion (Preliminary results)

• Conclusions and Future work


Motivation

Damage caused by collision, grounding or violent interaction with severe sea environment leads to flooding of water in ships

Maritime disasters have resulted in catastrophic loss of lives and has motivated various studies on dynamics of ship flooding

Estonia (1994)

Costa Concordia (2012)


Outline

• Motivation


• Experiments






Ruponen (2007) describes flooding stages after a damage as follows-

Flooding in damaged ships

Initial transientflooding

Steady StateProgressive flooding

Heel Angle

Time

Damage at midships more critical (Chang et al (1999))


Harbor

Open Sea

Resonance scenarios in damaged ships

Kong et al. (2009) numerically studied resonance phenomena for damaged ships in beam-sea waves

Sloshing: Sloshing refers to movement of a liquid inside a closed tank of a moving object

Piston mode resonance: Resonant fluid motion in vertical gaps within structures or between two structures can lead to vertically oscillating fluid

Inflow/Outflow


Outline

• Motivation


• Experiments






Experiment setup

WavemakerBeach

WP3 WP4

WP1 WP2

DamageDamage


Experiment conditions

Forced heave motions― Steady state conditions

Tests in regular waves― Steady state conditions― Transient flooding

Wavelength

Amplitude

Filling Depth h

Heave amplitudeHeave period

Compartment Breadth

Beam-sea conditions


Outline

• Motivation


• Experiment setup






Forced heave motions: High filling depth

High Filling depth


Forced heave motion: Shallow filling depth

In shallow water conditions, wave scenarios are different compared to higher filling depths

Flow phenomena are similar to those observed in closed tanks by Lugnifor forced oscillation in sway

Shallow filling depth


Effect of airtight compartment Air compression is significant in case of

― Sudden flooding― Small vents

It results in― Slower and lesser flooding

Piston mode absent

Change in sloshingbehaviour

Top Open

Non dimensional Frequency

Internal Waveamplitude

Heave amplitude


Outline

• Motivation


• Experiments






As compared to full compartment flooding, in asymmetric conditions –

Roll motion is smaller and sway motion is larger

Sloshing and piston mode frequencies increase

Effect of sloshing on ship motions is reduced

Wave period

Effect of asymmetric flooding


Initial transient flooding Most crucial for flooding- capsizing takes place during or immediately after this

phase

Time to flood depends on― Opening height relative to free surface― Initial stability― Wave period

Wave elevation(m)

t/T

Time to flood


Outline

• Motivation


• Experiments






Numerical method: Preliminary results

Blue (Water)

Red (air)

Green (transition region)

2D framework for a simplified section with main dimensions identical to experiments

Chamfers not included in the geometry for simulations


Forced heave motion: High filling depth

Qualitatively, the same wave scenarios are observed as in the experiments

Experiments

Numerical method


The results for internal and external wave elevation are consistent with experiments

Forced heave motion: Shallow filling depthExperiments

Numerical method


Outline

• Motivation


• Experiments






Experiments for a

damaged midship

section in beam-sea

waves

DD numerical method

Parameter investigation

Validation and verification

Parametric investigation of effects

such as –

• Progressive flooding

• Internal obstacles

Time to flood/capsize for a real

ship scenario

Conclusions and Future work

Example in waves


Thank you for your attention!

Questions?


Acknowledgement

Prof Greco and Prof Faltinsen for their help with thepresentation

Prof Lugni for their help with experiments

Finn , Yugao and Shaojun for their advice and providing materials relating to HPC


References

• Chang, B-C., (1999). On the damage survivability of Ro-Ro ships investigated by motion simulation in a seaway. Schiffstechnik-Ship Technology Research 46, 192–207.

• Faltinsen, O.M. and Timokha, A.N., (2009). Sloshing. Cambridge University Press.

• Kong, X.J. and Faltinsen, O.M., (2010). Piston mode and sloshing resonance in a damaged ship. OMAE.

• Palazzi, L. and deKat, J., (2004). Model experiments and simulations of a damaged ship with air flow taken into account. Marine Technology 41(1), 38–44.

• Ruponen, P., (2007). Progressive flooding of a damaged passenger ship. PhDThesis, Helsinki University of Technology.

• Shao, Y.L. and Faltinsen, O.M. (2012).Towards efficient full‐nonlinear potential‐flow solvers in marine hydrodynamics. Proceeding of the 31st International Conference on Ocean, Offshore and Arctic Engineering (OMAE), Rio De Janeiro, Brazil.


Real Ships

Breadth 25m

Normalization factor 1,129385

Range of normalized freq in Expts

0,35 0,309903

2,5 2,213594

Range of Time period from Expts to Real

ships 20,27467s

2,838454s

Intact

Water plane area 0,2875 m2

Restoring coefficient in heave 2817,5

Displacement at 14 cm 39,9 kg

Added mass coefficient 1

Added mass 39,9

A33+M33 79,8

Natural frequency in heave 5,941970847

Natural heave period 1,057424459 s

Damaged

Water plane area 0,085 m2

Restoring coefficient in heave 833

Displacement at 14 cm 39,9 kg

Added mass coefficient 4,2 ???

Added mass 167,58

A33+M33 207,48

Natural frequency in heave 2,003707764

Natural heave period 3,135779288 s

Experimental and numerical analysis of a damaged ship ...

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