Author Topic: WS Directional Analysis - MIKE BW  (Read 160 times)

tjhnsn

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WS Directional Analysis - MIKE BW
« on: May 17, 2020, 11:15:02 am »
Hi,

Hoping somebody may be able to give me a little insight into applying the directional spectral analysis tool to MIKE BW outputs.

I have a situation where I am trying to analyse wave conditions in the corner of two reflective revetment structures. However, due to the reflections, the total wave energy is substantially higher than the incident direction as is expected. The model has been run with directional random waves.

I am trying to apply the WS Wave Directional Analysis tool using the n,u,v MEM spectral analysis method to analyse incident and reflected energy, however the spectrum is giving me very little insight into this. All the energy (including reflected energy) appears to be predominately coming from the incident direction.

Is anybody aware of the theoretical background and the potential limitation to applying this analysis in reflective conditions like these? It should be noted that there appears to be a strong pattern of standing waves close to the revetments and I have analysed a location where constructive interference appears to be taking place.

Thanks,
Toby

tjhnsn

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Re: WS Directional Analysis - MIKE BW
« Reply #1 on: May 18, 2020, 12:07:23 am »
After doing a bit more research, I believe this comes down to an issue of phase locking occurring between the incident and reflected waves. This is a violation of the requirement around random phase angles in most Directional spectral analysis algorithms. Something that seems to be a challenge even in field measurements. Great little excerpt in Chapter 10.4.2 of Random Seas and Design of Maritime Structures (Goda) that enlightened me to this.


I guess the lesson to learn here is to be careful of directional spectra in highly reflective environments. Any other suggestions to try and separate reflected energy from the results would be more than welcome however :)
« Last Edit: May 18, 2020, 12:11:02 am by tjhnsn »