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Loads Induced on Ship Structures by Rogue Waves

Sally DenchfieldSchool of Engineering Sciences, University of Southampton, UK

Supervisors Prof. P. Temarel and Dr. D. Hudson

Fluid Structure Interactions

Research Group

Background

Acknowledgements

This project is supported by funds from theLloyds Register Educational Trust, through theLloyds Register University TechnologyCentre

Of increasing importance in the marine industry are rogue waves and the effect theyhave on marine structures.

Concern has grown following the loss of some ships due to apparent rogue waveencounters, and more famously the recorded impact of the NewYear Wave on theDraupner oil platform on 1st January 1995.

Figure 1: Photographed rogue wave encounters

Classification of a Rogue Wave

0.2H

HAI

S

max

2.1HCI

S

max

0.10H

LLI

max

OA

With respect to the surrounding sea state:

With respect to the encountering ship:

Methodology

Selected Rogue Wave Models

Wave-Structure Interactions2D linear hydroelasticity

Good agreement at low speeds

2D linear hydroelasticity over-predicts maximum heave and pitch at high speeds

Isolated rogue wave: NewWave

2

1

max

cos

N

n

nn tS

t

Rogue wave in a random sea: Optimised seaway

N

n

optfnnn xktA1

cos

Figure 5: Comparison of linear NewWave theory andexperimental results

Figure 6: Comparison of linear optimised seaway andexperimental results

Figure 2: Definition sketch of a rogue wave

Figure 3: Variation of LI with LOA

ttpcCtpbBtpaAee

Figure 9: % Increase in maximum heave withforward speed in optimised sea

Figure 10: % Increase in maximum pitch withforward speed in optimised sea

Influence of Rogue Wave on a Ship

Figure 11: Slamming and green water effectsduring rogue wave encounter at operational speed

Figure 12: Real-life rogue wave encounter showingequivalent situation to Figure 11

Figure 4: Methodology for research

Based on a wave spectrum

Can scale to requiredmax

Can be extended to higher orders

Suited to a comparative analysis

Based on a wave spectrum

Statistical properties maintained

during optimisation process

Solution dependant on initial(random ) phases

Can extend to include nonlineareffects

Figure 7: Variation in maximum heave withmaximum wave height for irregular, NewWave

and optimised seas at zero speed

Figure 8: Variation in maximum pitch withmaximum wave height for irregular, NewWave

and optimised seas at zero speed