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

No convergence in UZD

Susana Baston, modified 8 Years ago.

No convergence in UZD

Youngling Posts: 7 Join Date: 4/28/11 Recent Posts
Dear all,

I would like to know what to do when 'No convergence in UZD' appears. My simulation run 160 steps and this warning appeared 246 times.

Thank you very much in advance.
Rafael Casares, modified 8 Years ago.

RE: No convergence in UZD

Youngling Posts: 17 Join Date: 12/9/11 Recent Posts
Yeah! I have the same question.
Susana Baston, modified 8 Years ago.

RE: No convergence in UZD

Youngling Posts: 7 Join Date: 4/28/11 Recent Posts
Page 171 of the Flow manual says that timestep must be decreased. I hope it helps.
Katherine Cronin, modified 8 Years ago.

RE: No convergence in UZD

Padawan Posts: 42 Join Date: 2/23/11 Recent Posts
Hi Susana,

Did you check that the Courant Number hasn't been violated?
Erik de Goede, modified 8 Years ago.

RE: No convergence in UZD

Youngling Posts: 13 Join Date: 1/7/11 Recent Posts
Dear Susana,

Delft3D-FLOW can generate a lot of warnings, but this is one of the few ones that is rather serious. You should adapt your model till this warning has disappeared.

This warning seems to appear twice in every time step (because Delft3D-FLOW applys a two-stage time integration method and comes with this warning every half time step). It's evident that this is a time step problem. So, check your Courant number via QUICKIN.

Then, there are two options:
a) The Courant number is too large in a large part of your model. Then, the time step should be reduced.
b) Locallya large Courant number occurs. This might be due to locally small mesh sizes or to a locally deep area. Then, you might play with the mesh size (increase it somewhat) to reduce the Courant number. In this way, the "time step" problem is circumvented by changing the "grid".

With kind regards,
Erik de Goede
Eduardo Neon, modified 1 Year ago.

RE: No convergence in UZD

Youngling Posts: 1 Join Date: 1/22/20 Recent Posts
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