intro story Coast / Estuary

Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 
 

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Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

 

Message Boards

wave modeling question

JC
Jun Cheng, modified 7 Years ago.

wave modeling question

Youngling Posts: 16 Join Date: 7/20/13 Recent Posts
Dear Deltares,
A few days ago, I posted a question for wave modeling. Recently I kind of figure that out, the original question was I found that when I compare the distribution of significant wave height computed from wave-tide coupling model and wave-alone model, (the wave model from the same data set, and the coupled tide model share the same grid and depth file with tide model). I found that the wave height from the coupling(more than 1 m) is way higher than that from the wave-alone model (about 0.2-0.3 m). Given that the wave at the boundary is only about 0.3m, and the influence of tide on wave height shouldn't be that significant, so it is more likely that the wave-current coupling model have something wrong.

What I recently found was that, since in my wave boundary file, the wavecon file was used with zero wind speed and wind velocity, what I found is that in the mdw file, under the ‘use hydrodynamic flow results' , 'hydrodynamics Option box', I choose the 'Don't use the Wind'. instead of the previously 'use but don't extend' Then I ran the wave-current coupling model again, the results become normal, the computed wave height distribution is about 0.3m now, instead of around 1.5m.

What I am still wondering is that if there is any reason I am doing this, as I already specify the wind field input as 10m/s uniformly in the MDF files, by doing 'don't use wind' I just ignore the wind process.

Thanks so much!
Jun
JC
Jun Cheng, modified 7 Years ago.

RE: wave modeling question

Youngling Posts: 16 Join Date: 7/20/13 Recent Posts
thus based on the observation above, I am wondering either the 10 m/s uniformly wind field is not proper, or in the wavecon file, the wind speed or direction should be properly given, instead of using zeros.
Am I right?
Jun
Emiel Moerman, modified 7 Years ago.

RE: wave modeling question

Padawan Posts: 84 Join Date: 3/10/11 Recent Posts
Hi Jun,

When you use a wavecon file, the parametric wave conditions in the MDF and the wind conditions are ignored and taken from the wavecon file instead.
So it doesn't matter if you have defined wind conditions to be 0 m/s or 10 m/s in the MDF, the wind conditions from the wavecon file are applied. So if you would like to force wind to your model when you make use of a wavecon file, you should define it in the wavecon file.

Regards,

Emiel
JC
Jun Cheng, modified 7 Years ago.

RE: wave modeling question

Youngling Posts: 16 Join Date: 7/20/13 Recent Posts
Hello Emiel,
The wind given in the wavecon files force the wind in the boundary condition, how about the wind field in the computational domain? Does another wnd file also need to be included ?
Regards
Jun
Renan Ribeiro, modified 7 Years ago.

RE: wave modeling question

Padawan Posts: 55 Join Date: 3/23/11 Recent Posts
Hi Jun,

I am glad you solved your problem. But even using the wind from hydrodinamic model the Hs shouldn't rise too much, unless the winds you are using are very strong.

Answering your question, the wind given in the wavecon files force the wind at entire domain, not only at boundary.

Regards,
Renan