DelwaqScale factor and units in Delwaq  Coast/Estuary  Delft3D
intro story Coast / Estuary
Coast / EstuaryCoastal 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 waveinduced 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. ** PLEASE TAG YOUR POST! **  Sub groups

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DelwaqScale factor and units in Delwaq
Gholamreza Shiravani, modified 2 Years ago.
DelwaqScale factor and units in Delwaq
Padawan Posts: 65 Join Date: 6/25/16 Recent PostsHi,
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 1e006 it is converged. I read the Manual of Delwaq and it was said that this factor is to Change the Units of DFLOW 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 DFLOW results are SI, it means the Dispersion unit is m2s1, velocity ms1, ... Does Delwaq convert the DFLOW automatically in m/d or grm3 (in comparison with kgm3) or we should apply the Scale factor by Dispersion? To make the Problem undestandable, what means a scale factor for additional vertical Diffusion of 1e007?
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 DFLOW turbulence model (kEpsilon)?
Why for small scale factors the model convergs?
Arjen Markus, modified 2 Years ago.
RE: DelwaqScale factor and units in Delwaq
Jedi Knight Posts: 223 Join Date: 1/26/11 Recent PostsThere 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 1.0e5 and the maximum number of iterations MaxIter to 1000. This may help the calculation to reach a converged state.