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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Iteration accuracy drops to NaN at some timesteps in wave alone runs, why?

George Victor, modified 1 Year ago.

Iteration accuracy drops to NaN at some timesteps in wave alone runs, why?

Youngling Posts: 7 Join Date: 5/19/17 Recent Posts
Hi everyone, I was doing a case study to understand the effect of increased wind velocity in wave generation, over a bay. As a part of this, 1. wave alone simulation was completed with actual wind data. Time and space varying wind components (U and V) were used for this. 2. Another wave alone simulation was done in a similar way, the only change made was by multiplying all the U-V wind component data with a factor 1.4.

The first run was completed successfully, however, in the second case, an issue is seen. It is to be noted that this was not popped up as an error. The issue is, at certain time steps the iteration accuracy value drops to" NaN", and as an effect, the desired output parameter values also drops to zero. Few things are to be noted on this behalf- a)no error message is showed and model keeps running fine, even after the issue b)the model continues to work well even in the very next time step. Later on, in few more time steps, the same issue reappears.

I checked the input files (U and V components) and made sure they're error free.

The "swn-diag" file was inspected and found that the only warning that came was " ** WARNING: Differences in wave height at the boundary. Relative difference between input and computation >= 0.10 ". However, this warning was also seen in timesteps that didn't show the aforementioned issue.
*swn-diag file is attached with this.

I doubt if the issue is a result of the inefficiency of the model in interpolating the wind parameters spatially. Picture showing the spatial spread of wind velocity ( magnitude) for 3 consecutive time steps are attached. (first time step when no aforementioned issue arose, while the second time step with the issue and the third time step which was again free of the issue.)

Why is this issue coming? How can I rectify it?

*wind components (meteo files) are also attached
Aravind kumar, modified 11 Days ago.

RE: Iteration accuracy drops to NaN at some timesteps in wave alone runs, w

Youngling Posts: 2 Join Date: 8/12/19 Recent Posts
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