Abstract
Stories of so-called freak waves (also known as monster waves and extreme waves) have long existed among seafarers. Typical of freak waves is that they are much larger than the surrounding waves, and thus appears to be unexpectedly large in the current sea conditions. Naturally, such extreme waves being a threat to ships and oil platforms. An important question to answer is whether there are special circumstances that increase the probability where freak waves should occur. This thesis examine how different characteristics of a sea state affects the number of freak waves. To investigate this, advanced mathematical models are used to 'simulate' movement on the ocean wave by using computers. From these numerical simulations, we can obtain information about the waves, and especially the probability of freak waves. We have found that the probability of freak waves depends strongly on the length of a typical wave crest is compared with the wavelength. If a typical wave crest is longer than 10 times the average wavelength, it is much higher chance of freak waves compared to more 'short combed' sea. In a subsequent study, we looked at the sea conditions in which two wave systems, a long wave swell and more
More>>
Citation Formats
Gramstad, Odin.
Weakly nonlinear dynamics of gravity waves.
Norway: N. p.,
2010.
Web.
Gramstad, Odin.
Weakly nonlinear dynamics of gravity waves.
Norway.
Gramstad, Odin.
2010.
"Weakly nonlinear dynamics of gravity waves."
Norway.
@misc{etde_1012711,
title = {Weakly nonlinear dynamics of gravity waves}
author = {Gramstad, Odin}
abstractNote = {Stories of so-called freak waves (also known as monster waves and extreme waves) have long existed among seafarers. Typical of freak waves is that they are much larger than the surrounding waves, and thus appears to be unexpectedly large in the current sea conditions. Naturally, such extreme waves being a threat to ships and oil platforms. An important question to answer is whether there are special circumstances that increase the probability where freak waves should occur. This thesis examine how different characteristics of a sea state affects the number of freak waves. To investigate this, advanced mathematical models are used to 'simulate' movement on the ocean wave by using computers. From these numerical simulations, we can obtain information about the waves, and especially the probability of freak waves. We have found that the probability of freak waves depends strongly on the length of a typical wave crest is compared with the wavelength. If a typical wave crest is longer than 10 times the average wavelength, it is much higher chance of freak waves compared to more 'short combed' sea. In a subsequent study, we looked at the sea conditions in which two wave systems, a long wave swell and more short wavy wind waves meet. We have investigated whether such circumstances, which are common on the sea, can lead to more freak waves. It turns out that the presence of a swell the number of freak waves somewhat (approximately 5-20%) compared with a similar situation without swell. The exception is if the two wave systems moving at right angles to each other, when we see minimal increase in the number of freak waves. This knowledge of freak waves can be useful for example when it comes to sound sea conditions where the probability of freak waves are believed to be greater than otherwise. In addition to the above numerical experiments, the thesis contains theoretical papers where some new and prepared models to describe wave motion mathematically, in the form of so-called weakly nonlinear models, is derived. Dissertation work has been performed at the Department of Mathematics, University of Oslo. (AG)}
place = {Norway}
year = {2010}
month = {Jul}
}
title = {Weakly nonlinear dynamics of gravity waves}
author = {Gramstad, Odin}
abstractNote = {Stories of so-called freak waves (also known as monster waves and extreme waves) have long existed among seafarers. Typical of freak waves is that they are much larger than the surrounding waves, and thus appears to be unexpectedly large in the current sea conditions. Naturally, such extreme waves being a threat to ships and oil platforms. An important question to answer is whether there are special circumstances that increase the probability where freak waves should occur. This thesis examine how different characteristics of a sea state affects the number of freak waves. To investigate this, advanced mathematical models are used to 'simulate' movement on the ocean wave by using computers. From these numerical simulations, we can obtain information about the waves, and especially the probability of freak waves. We have found that the probability of freak waves depends strongly on the length of a typical wave crest is compared with the wavelength. If a typical wave crest is longer than 10 times the average wavelength, it is much higher chance of freak waves compared to more 'short combed' sea. In a subsequent study, we looked at the sea conditions in which two wave systems, a long wave swell and more short wavy wind waves meet. We have investigated whether such circumstances, which are common on the sea, can lead to more freak waves. It turns out that the presence of a swell the number of freak waves somewhat (approximately 5-20%) compared with a similar situation without swell. The exception is if the two wave systems moving at right angles to each other, when we see minimal increase in the number of freak waves. This knowledge of freak waves can be useful for example when it comes to sound sea conditions where the probability of freak waves are believed to be greater than otherwise. In addition to the above numerical experiments, the thesis contains theoretical papers where some new and prepared models to describe wave motion mathematically, in the form of so-called weakly nonlinear models, is derived. Dissertation work has been performed at the Department of Mathematics, University of Oslo. (AG)}
place = {Norway}
year = {2010}
month = {Jul}
}