Modelling Rivers


Rivers are natural water courses. They have vital contributions to the social and economical welfare of societies living along their course. They provide continuous, usually dependable, flow and supply of water. Accordingly, centralised civilisation began emerging independently along number of river valleys; e.g. the Nile, Tigris and Euphrates, the Indus and the Yellow Rivers. Since then, mankind has been in continuous struggle to understand and live in harmony with this gift/force of nature. Modelling rivers is the modern way to understand their behaviour and is an essential tool to tackle several river problems.

Delft3D is the state-of-the-art modelling framework for hydrodynamics, water quality, ecology, waves and morphology.
Here, in this space, we share knowledge & experiences, and discuss issues related to modelling of rivers.





Sub groups
D-Flow Flexible Mesh
Cohesive sediments & muddy systems


Message Boards

Results stored by Delf3D from SWAN

Samantha Maticka, modified 2 Months ago.

Results stored by Delf3D from SWAN

Youngling Posts: 6 Join Date: 10/2/20 Recent Posts
I'm trying to understand what results are actually written from SWAN, when delft3d runs a SWAN simulation. I've done some tests to compare, and it is still not clear. I'll say what I think I understand, and the tests I ran, and hope that someone can explain the rest!

In the *.mdw file I specify TimePoints, TimeStep, and COMWriteInterval. The TimePoints determine when to run and record results from SWAN. For me they are 0, 3, and 6 hours. The TimeStep and COMWriteInterval appear to control the timestep and time interval that each SWAN simulation is run for. I vary these values in my tests, but for example, a TimeStep of 60 min and COMWriteInterval of 180 min produces a SWAN simulation performed from (for TimePoint=0hr) 0 hr to 3 hr in increments of 1 hr, and then (for TimePoint=3h) from 3 hr to 6 hr in increments of 1 hr. 

Specifically, my question is 'which SWAN time step calculation is actually stored, per TimePoint simulation that is conducted?' For example, at TimePoint=0h, is the data that is produced after 1 timestep recorded (1 hour for example above)? at the end of the simulation (3 h for example above)? something else?

The problem for me is that in all of my simulations, each SWAN run does not converge until the 3rd timestep taken by SWAN (the 1st and 2nd end around 70% and 80% accuracy after 15 iterations), no matter the size of the timestep taken (30, 60, 180 min) so I would only want delft3D to retain data produced after the 3rd timestep. 

I ran some tests where I varied both TimeStep and COMWriteInterval to see how the results of significant wave height varied. I found the only way to get the same results between 2 simulations was to have the same TimeStep (COMWriteInterval) did not make a difference.

For reference, the tests I ran wereTimeStep (minutes) : COMWriteInterval (minutes) as,

30 : 60

30 : 180

60 : 60

60 :180

180 : 180

Any insights into how data is stored from SWAN would be super helpful. I get results for hour 0, so I thought there must be some sort of assignment of data produced from a later time to the TimePoint of interest. 

Thank you in advance for any and all help with this emoticon

Best Regards,