EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The long-time spatial and temporal development of Triadic Resonance Instability

Katherine Grayson, Stuart Dalziel, and Andrew Lawrie
Katherine Grayson et al.
  • University of Cambridge, Department of Applied Mathematics and Theoretical Physics

How to cite: Grayson, K., Dalziel, S., and Lawrie, A.: The long-time spatial and temporal development of Triadic Resonance Instability , EGU General Assembly 2020, Online, 4–8 May 2020,, 2019

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Presentation version 1 – uploaded on 29 Apr 2020
  • CC1: Comment on EGU2020-1584, Géraldine Davis, 07 May 2020

    Thank you very much for uploading these very interesting experimental results.
    I have mainly two questions :
    * How do you manage to not get many reflexions on the boundaries of the tank at long time (only one is visible on your plots, is that generic) ? Because if you get multiple reflections it could natturally lead to an amplitude modulation (linear response of a cavity away from a resonance frequency).
    * Do you observe a modulation in the frequencies of the two secondary waves (you could see this via ploting a spectrogram for instance) ? Because I ran some experiments in another geometry (2D-attractor) and I was very often seing a slow oscillation of the secondary wave frequencies --> if the filter you use to get psi1 and psi2 has a smaller width than the excursion of the secondary wave frequencies this could be link to the oscillations of psi1 and psi2.
    Anyway it is great to investigate the theoretical results of TRI with some nice experiments as you do :)
    Géraldine Davis

    • AC1: Reply to CC1, Katherine Grayson, 07 May 2020

      Hi Geraldine,

      Thank you for your insightful questions!  To answer:

      1. In terms of reflections, we are fortunate enough to have an 11m long tank over which we conduct experiments. Due to the location of the wavemaker, the wave beam travels nearly 7m before interacting again with the original experiment. At this point , due to viscosity, it will have decayed to around 5% of its original amplitude. While this is very small, it is not completely negligible and the next experiments we want to run (when the lab reopens!) is to direct the wave beam in the opposite direction, where it will have around 32 m over which to travel before interacting with the primary beam. This way we can confirm that it is not end wall reflections that are causing this effect.
      2. This is true, in addition to the oscillations of the amplitude I also see a slow modulation in the frequency of the two resonant waves. I haven’t included that graph but I can see if I can upload, the modulation of the frequency appears to follow the amplitude oscillations for the resonant waves. I have filtered across a small range of frequencies to obtain the amplitudes so there seems to be some coupling between the amplitude oscillation and the frequency oscillation. Interesting that you are seeing the same effect, perhaps by just assuming two fixed resonant wave vectors and frequencies you do not capture the full instability.

      Let me know if I have answered your questions, I’m looking forward to the chat tomorrow, your experiments look very exciting!