| Abstract: |
| Despite centuries of study, there continue to be many open problems in dynamics of water waves. One such problem is that of frequency downshifting, a phenomenon in water waves where the spectral peak and/or mean of the wave spectra permanently moves downwards over the wave`s evolution. Typically this phenomenon is argued to be primarily driven by dissipative processes such as wavebreaking, with energy loss being the only pathway to permanent spectral movement. However, recent work by the authors have demonstrated that this phenomenon can happen conservatively (i.e. without energy loss) and can be mediated by wave-mean flow interactions. Since both processes are shown to contribute to downshifting, and both are present within water wave problems, this provokes the natural question - how do they interact and contribute to the overall process of downshifting in water waves?
This talk will start with an overview of downshifting from a wave-mean flow perspective in order to demonstrate how such a process mediates downshifting, by using a Benney-Roskes system to illustrate the fundamentals of the process. We will then introduce (simple) dissipative effects and explore how this impacts movements in the spectral peak as a function of nondimensional depth. Ultimately we find that deep into the modulationally unstable regime dissipation leads to more monotonic and narrow-banded downshifting than that driven by purely mean flow effects, suggesting that dissipation plays a long-term role in arresting the downshifting phenomena. |
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