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. 




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



Message Boards

numerical instability in domain decomposition with inclined bathymetry

Markus Gross, modified 2 Years ago.

numerical instability in domain decomposition with inclined bathymetry

Youngling Posts: 7 Join Date: 12/10/11 Recent Posts



We are trying to run a domain decomposition model but run into several difficulties. Attached one of our problems as Smallest Possible Case.


It is a cut out rectangle and inside it is a higher resolution grid with a 1:3 ratio.


It is currently setup as spherical, but I converted it into Cartesian at some point and it did not change anything. We also tried the recent trunk version.


In this case there are no open boundaries. So everything should stay within the numerical noise of the solver. The bathymetry is inclined, with a constant gradient.


In a relatively short period it spins up a significant instability, originating from the domain decomposition boundary, which eventually leads to model failure. For me:


 Time to finish   2m 14s,   33.5% completed, time steps left  766
 Flow exited abnormally


We must be missing something obvious, but with now two weeks of searching I cannot find it.


Does anybody have any advice? Is there something really silly in the setup?


I feel that without resolving this, going to more complex bathymetries and boundary conditions would not make any sense.


Any help/advise would be greatly appreciated!!


Best wishes,



Frank Platzek, modified 2 Years ago.

RE: numerical instability in domain decomposition with inclined bathymetry

Youngling Posts: 3 Join Date: 3/24/11 Recent Posts

Hi Markus,

Thanks for your post. I will have a look at your model to see what goes wrong.

Best regards,