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

Advice for setting up a morphol. model: DD vs. NestHD (vs. FM)

Roland Hesse, modified 4 Years ago.

Advice for setting up a morphol. model: DD vs. NestHD (vs. FM)

Youngling Posts: 21 Join Date: 11/21/14 Recent Posts
Dear all,

I am relatively new to Delft3D. I have started working on a project concerning the sediment transport and morphology in a big estuary. An existing Delft3D 3D-model (10 Layers, curvilinear grid, 2 Domains, approx. 60 000 elements) shall be adjusted. The overall aim is reproduce net sediment deposition within a “focus area”. Morhological structures (e.g. ripples, dunes) are not of explicit interest. A scratch of the grid with the marked focus area is attached. So far only “Hydrodynamics” and “Salt” are implemented with corresponding boundary conditions (time series for tide; river discharge). Due to quite long run-time even for the so far implemented processes (approx. 2 hour run-time for 1 day of simulation using DD on a PC: 16 GB RAM; 7 CPUs @ 3,60 GHz) there is need for run time optimization. This should be done by reducing the resolution outside the focus area. As far as I learned from the manual and in this forum there are basically 2 options in Delft3D to achieve this:

A) Domain Decomposition (DD)
- same depth at DD-boundary
- same time step for all domains
emoticon NestHD (“nesting”)
- offline coupling/ no feedback from finer to the coarser grid
- same number of layers for all grids

I am aware that there are more aspects, but I listed these “disadvantages” as in my point of view these might be crucial for this research. I tend to use DD as I think that online coupling might be necessary to model sediment processes (e.g. turbidity zone). Besides the possibility of 2D and 3D Domains with DD might be helpful. A third option could be D-Flow FM. Though, I am not sure if it is already available with the same options (morphology module etc.) as are implemented in the current DELFT3D-Flow.

Could anyone give me some advice or share his/her experience? Particularly, I would be interested in using sediment transport (probably all fraction types “mud”, “sand” and “bedload”) and morphological updating with DD. Are there problems at the DD-boundaries? Are there advantages using NestHD instead of DD? Might D-Flow FM be a full functional alternative?

kind regards,

Sujan Baral, modified 3 Years ago.

RE: Advice for setting up a morphol. model: DD vs. NestHD (vs. FM)

Youngling Posts: 4 Join Date: 6/11/16 Recent Posts
Hi Roland,

Can you upload your .mdf, .mdw and .sed file so that I can get the picture of what you are trying to do?