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



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Delwaq-Scale factor and units in Delwaq

Gholamreza Shiravani, modified 1 Year ago.

Delwaq-Scale factor and units in Delwaq

Padawan Posts: 65 Join Date: 6/25/16 Recent Posts


to prepare a Scenario using define Input, we have an Option with the Name of "Dispersion", and here  is " Additional vertical Diffusion", I selected the "Use results from hydrodynamics" and "Scale factor" is 1 but model is not converged but for a low scale factor like 1e-006 it is converged. I read the Manual of Delwaq and it was said that this factor is to Change the Units of D-FLOW results in such a way to correspond the Delwaq calculations. However, using IM (inorganic Matterial) it Needs settling velocity as m/d (meter per day) and D-FLOW results are SI, it means the Dispersion unit is m2s-1, velocity ms-1, ... Does Delwaq convert  the D-FLOW automatically in m/d or grm-3 (in comparison with kgm-3) or we should apply the Scale factor by Dispersion? To make the Problem undestandable, what means a scale factor for additional vertical Diffusion of 1e-007?

Why for such scale factor Delwaq converges but for higher values, e.g. 1,  it does not converge?

When I need a scale factor?

Does scale factor only chanage the Additional vertical Diffusion, which was calculated already through D-FLOW turbulence model (k-Epsilon)?

Why for small scale factors the model convergs?

Arjen Markus, modified 1 Year ago.

RE: Delwaq-Scale factor and units in Delwaq

Jedi Knight Posts: 223 Join Date: 1/26/11 Recent Posts

There is some misunderstanding here. The scale factor for the vertical dispersion/diffusion is really a scale factor for that parameter only. In the "raw" input you can use scale factors in several locations to facilitate conversion from one unit (the one you find in reports for istance) to another (the one used by the DELWAQ calculation itself). That is what the documentation is referring to or should refer to.

The flow field is read as is and the proper units are m3/s for the flow, m2 for the area and m3 for the volume.

The problem you are facing wrt the stability/convergence has to do with the iteration parameters. The GUI puts in default values, but sometimes you need different ones - try increasing the threshold Tolerance to 1.0e-5 and the maximum number of iterations MaxIter to 1000. This may help the calculation to reach a converged state.