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

Velocity sign in boundary conditions

RC
Rafael Casares, modified 8 Years ago.

Velocity sign in boundary conditions

Youngling Posts: 17 Join Date: 12/9/11 Recent Posts
Hi, I am modeling an estuary and I am defining boundary conditions at some distance far away from the mouth.

I defined a long-shore water level boundary together with 2 cross-shore current boudaries, but the question is how to get the long-shore currents to be in one direction or in the other? Actually, ocean currents are southward.

I suppose that one current boundary should have velocities with a positive sign and the other with a negative sign. Is there any rule instead of trying and see what happens?

Regards
U
Juliane Büttner, modified 8 Years ago.

RE: Velocity sign in boundary conditions

Hello,
I did not find a good description in the manual, so I tested the behaviour. From my results, I understand that:
Normal velocity is not defined inward and outward, but positive to the East and negative to the West and negative to the north and positive to the south.
Please correct me if I am wrong!

Best regards,
Juliane
Bert Jagers, modified 8 Years ago.

RE: Velocity sign in boundary conditions (Answer)

Jedi Knight Posts: 201 Join Date: 12/22/10 Recent Posts
Hi,

Velocities, discharges, transport rates are positive when they indicate movement in positive M or N direction, and negative when they indicate movement in negative M or N direction. Depending on your grid orientation the positive values may correspond to East and North directions (this is the case for the default orientation of a rectangular grid created using RGFGRID), but it could be any other direction. So, the guiding principle is the grid numbering!

Note that this will obviously be different for the upcoming unstructured grid/flexible mesh version since such a mesh usually doesn't have a consistent grid numbering.

Cheers,

Bert
RC
Rafael Casares, modified 8 Years ago.

RE: Velocity sign in boundary conditions (Answer)

Youngling Posts: 17 Join Date: 12/9/11 Recent Posts
That's right, thank you very much, Bert!

The upcoming mesh version will be for Delft3D too?

Regards,

Rafael