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intro story DELWAQ

DELWAQ

DELWAQ is the engine of the D-Water Quality and D-Ecology programmes of the Delft3D suite. It is based on a rich library from which relevant substances and processes can be selected to quickly put water and sediment quality models together.

The processes library covers many aspects of water quality and ecology, from basic tracers, dissolved oxygen, nutrients, organic matter, inorganic suspended matter, heavy metals, bacteria and organic micro-pollutants, to complex algae and macrophyte dynamics. High performance solvers enable the simulation of long periods, often required to capture the full cycles of the processes being modelled.

The finite volume approach underlying DELWAQ allows it to be coupled to both the structured grid hydrodynamics of the current Delft3D-FLOW engine and the upcoming D-Flow Flexible Mesh engine (1D-2D-3D) of the Delft3D Flexible Mesh Suite (or even other models such as TELEMAC).

'DELWAQ in open source' is our invitation to all leading experts to collaborate in further development and research in the field of water quality, ecology and morphology using Delft3D. Feel free to post your DELWAQ related questions or comments in this dedicated forum space. If you are new to DELWAQ, the tutorial (in the user manual) is a good place to start. A list of DELWAQ related publications is available here.

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Sub groups
D-Flow Flexible Mesh
DELWAQ

Cohesive sediments & muddy systems

 


Message Boards

WAQ Coupling

NJ
Nick Jewitt, modified 5 Years ago.

WAQ Coupling

Youngling Posts: 3 Join Date: 1/4/15 Recent Posts
Hello,

I have tried the same flow model with two separate time steps. When I try to couple the hydrodynamics with WAQ, the com file does not include the defined start and stop times defined in the flow procedure but instead converts to the same day but at hour 24. Example:

Flow Start: 17 04 2014 00 00
Flow Stop: 24 04 2014 00 00

When opening the com file in WAQ coupling

Couple Start: 16 04 2014 24 00 00
Couple Stop: 23 04 2014 24 00 00

When I change them to be the "correct" value indicated in the flow start and stop, I then get the error that the stop time of conversion must be at or before the stop time of the coupled hydrodynamic database. If I leave it, I get the error that there are imprper values in the date/time fields.

This only happens when I use the magnitude lower timestep in flow of 0.001 compared to the normal 0.01 where I don't get the above error but have more velocity change errors.

Any suggestions?

Thanks in advance,
Nick
AM
Arjen Markus, modified 5 Years ago.

RE: WAQ Coupling

Jedi Knight Posts: 223 Join Date: 1/26/11 Recent Posts
This is most probably due to rounding errors in the computation of the number of seconds from timestep in minutes that is used within Delft3D-FLOW (this is a floating-point number and that may cause such issues, though this is a new one in the 20+ years I have been dealing with the coupling FLOW-WAQ).

A possible workaround: let the FLOW calculation continue slightly further than 24 september 0:00. A single minute may be enough. Then the time you specify and which is consequently converted time is at least within the available range. Let us know if this solves the problem. Also if it does not, because then we will have to dig deeper.
MJ
Michel Jeuken, modified 5 Years ago.

RE: WAQ Coupling (Answer)

Jedi Knight Posts: 156 Join Date: 1/21/13 Recent Posts
Hi Nick,

That is strange behaviour. My first suggestion would be to skip the com-file for WAQ, and to write the WAQ input directly. This can be switched on on the Output section of the FLOW GUI. Switch on Export WAQ input, and go to "Edit WAQ inpit >>" to specify the periods/interval

Michel
AM
Arjen Markus, modified 5 Years ago.

RE: WAQ Coupling (Answer)

Jedi Knight Posts: 223 Join Date: 1/26/11 Recent Posts
Argh, I should have checked the source code:

Rather than comparing the actual _date and time_, the GUI compares the _internal string representation_ of the date and time. This gives the correct result, EXCEPT for the equivalence of day+24 hours and day+1 and 0 hours.

So, the error message has nothing to do with FLOW using a floating-point number for the timestep (well, that is in the 24 versus 0 hours issue). If you let the FLOW calculation continue just a wee bit, the GUI should be forced to do the right thing.
NJ
Nick Jewitt, modified 5 Years ago.

RE: WAQ Coupling

Youngling Posts: 3 Join Date: 1/4/15 Recent Posts
Thanks!

I will try both possible solutions.

Nick