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Isolating Long Waves

JW
Johnathan Woodruff, modified 1 Year ago.

Isolating Long Waves

Capillary Posts: 5 Join Date: 2/22/19 Recent Posts

Hello,

 

I am running a simple 1D model in jonswap mode, and I want to isolate the long waves being resolved by the model. I am outputting H and zs from my model. From what I understand H is only contributed to by the shortwaves and zs is contributed to by tides and infragravity waves. I am not running tides in my model, so would the zs value just be the infragravity waves? Please correct any incorrect assumptions I have made. Thanks in advance! Attached in an XBlog from one of my runs.

 

Johnathan Woodruff

Attachments:

MD
Menno de Ridder, modified 1 Year ago.

RE: Isolating Long Waves

Capillary Posts: 4 Join Date: 9/18/18 Recent Posts

Hi Johnathan,

That is correct. The H is the Hrms based on the instantaneous wave energy. The long waves (and tides) are resolved with the flow model, which is indeed given by zs. If you need the wave height (for example Hrms) of the long waves, you have to compute it from the water level signal (zs). Be aware that there exist a Matlab toolbox which can also transform the water level signal to a wave height. See https://xbeach.readthedocs.io/en/latest/tools.html.

Cheers,

Menno

JW
Johnathan Woodruff, modified 1 Year ago.

RE: Isolating Long Waves

Capillary Posts: 5 Join Date: 2/22/19 Recent Posts

Hey Menno,

 

Thank you for your quick response! I was looking through the XBeach_v1.23.5527_XBeachX manual and found an output named "bi". I think this will give me the long wave height I am looking for. Am I correct in this assumption? Thank you!

 

JW
Johnathan Woodruff, modified 1 Year ago.

RE: Isolating Long Waves

Capillary Posts: 5 Join Date: 2/22/19 Recent Posts

Menno,

 

I found that it is much easier to just use the matlab toolbox to extract the infragravity waves with the kings day version of xbeach. Thank you for you help!

 

Johnathan Woodruff