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RE: Wave length and depth limitation (kd>1)

GB
Georgii Bocharov, modified 2 Months ago.

Wave length and depth limitation (kd>1)

Capillary Posts: 1 Join Date: 12/19/16 Recent Posts

I have been trying to run XBeach for short waves (Tp<3sec, Hs<1m) in non-hydrostatic mode to model wave transformation towards shallow water. For design depths (30m) the model was not stable and pushed all energy to lower frequencies (<.2Hz). I read that the nonlinear shallow water equations solved in the NH mode are accurate only up to kd<1 (waveslengths to longer than ~1/6 of depth). I also read in the manual here https://oss.deltares.nl/documents/48999/49476/non-hydrostatic_report_draft.pdf (page 23) that vertical resolution would need to be boosted for kd>1.

 

My question is: how do I boost vertical resolution?  If its not possible, then is there a way to model waves with kd>1 in XBeach?

Arnold van Rooijen, modified 2 Months ago.

RE: Wave length and depth limitation (kd>1)

Swell Posts: 239 Join Date: 11/7/11 Recent Posts

Hi Georgii,

 

You are correct that your waves seem to be a bit too much like 'deep water waves' for XBeach (i.e. the kd-value too high). You may be able to use the quasi 2 layer option of XBeach (keyword nonhq3d), but I expect this may still not get you there.

XBeach does not offer the option to increase the vertical resolution, so in that case you may want to consider using the SWASH model by TU Delft (http://swash.sourceforge.net/)

Cheers

Arnold