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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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D-Flow Flexible Mesh
DELWAQ

Cohesive sediments & muddy systems

 


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Coastal model Dissolved Oxygen (DO) boundary & computational issue

DK
Danker Kolijn, modified 5 Years ago.

Coastal model Dissolved Oxygen (DO) boundary & computational issue

Youngling Posts: 10 Join Date: 11/4/14 Recent Posts
For my coastal scenario (3 open boundaries, large volume of water with north/south alongshore currents) I experimented with the SWRear settings where 7,9,10 (see various time-series) were recommended to compute a diurnal DO signal using temperature and cloud cover, etc. . However, when I imposed an average value of 6.7 mg/L (as a time series) at the boundary the model did not produce the proper output (dotted red line does not produce amplitude expected) when compared to measured (black line). It seems almost as if the flow of DO from the boundary damps the computational process (I confirmed this in a video of the simulation). When I implemented a -999 DO time-series at the boundaries I found that this is equivalent to introducing 0 mg/L of DO (red dots on plot), where the model seems to be initially inundated with low DO. However, it then starts to the generate the proper signal (in phase and somewhat reasonable amplitude) when compared to my measured data.



I feel like i'm missing something very simple. I don't want to impose a measured DO boundary condition. I want the model to compute DO on it's own given the temperature and climatic conditions I feed the model. Does anyone know why when I input a higher average DO at the boundary, the computational process of generating a diurnal DO concentration seems to be damped?
many thanks in advance
CT
Christophe Thiange, modified 5 Years ago.

RE: Coastal model Dissolved Oxygen (DO) boundary & computational issue

Jedi Knight Posts: 125 Join Date: 11/15/12 Recent Posts
Hi Danker,

It looks indeed like your boundary conditions are dominating the solution here.
What is the average age of water in your domain?
Is the flow direction at the boundaries mainly constant or does it change regularly?
Are you using any timelags with your boundary conditions?

The fact that your runs with zero DO at the boundaries yield a signal with more amplitude is likely due to the fact that the reaeration rate also depends on the difference between actual and saturation DO concentrations.

Christophe