Mathieu Hellegouarch

Hi,

If you want to model an overflow structure, I think the easiest way is to only represent the ground level in the mesh (without buildings), and then add these overflow structures as "dikes". This kind of structure can be defined under the "Structures" menu in the MIKE 21 FM setup.

If that doesn't fit your needs, you can also represent the buildings with higher elevations within the buildings' extent : this solution may however require a longer processing time depending on the number of buildings. This can be achieved either by editing the scatter data in the Mesh Generator (use the dedicated icons from the upper toolbar) or you can create a mesh file without buildings, and edit manually this mesh file afterwards by opening it with "Data Manager".

Let us know if you need further explanations about these options.

Best regards,
Mathieu

Hi Ben,

Yes, that seems to be due to instabilities. If you get warings in the log file indicating that bed levels are different at rivers' junctions, then you should indeed try to correct these discrepancies of bed levels. To do that, you can indeed add cross sections at river junctions, and then adjust their levels.

You can also look at the results at the first time steps: if there is a big change in the results between the initial conditions and the following time steps, it may also be cause of instabilities. In that case, this has to be avoided by improving the initial conditions.

There are other things that can help to improve the stability, but an important one is the time step: depending on the spatial discretisation and the geometry of the river, you may need to decrease the time step to e.g. 1 s. So you can also consider reducing this time step, for example if you kept the default value.

Best regards,
Mathieu

Dear Razieh,

It seems that the problem is that you entered wrong coordinates. There are actually two kind of coordinates in MIKE 21:
- the so-called j;k coordinates, which respectively describe the column and row numbers for a given cell.
- the actual XY coordinates expressed in the coordinate system you have defined in the bathymetry file.

The coordinates used to locate a structure are the actual XY coordinates, but you have apparently typed the j;k coordinates. So that would explain why MIKE 21 considers that the structure isn't within the domain.

So you probably need to change these coordinates in the "Location" window. To get these coordinates, open the bathymetry file, go to View \ Mouse Pointer Coordinates, and select Map Projection Coordinates. When you fly over the map, the XY coordinates are now displayed in the lower part of the screen, along with the j;k coordinates.

After editing the coordinates in MIKE 21 for the structure, don't forget to change the "Projection" and select the same map projection as the one defined in the bathymetry file.

Best regards,
Mathieu

Hi Razieh,

It seems that you have a problem in the definition of the output file: indeed a time series is located with a single J and a single K coordinate. So you should only have one value in both the J and the K columns, but in your case you have 2 values separated by a comma. You should try to apply only one value and see if it works.

Note that you can click on the "..." button between the 'Time ' and 'Data file' columns, which will open a new window in which it's easier to type the coordinates and time steps.

Finally, the reason why you only get one time step in your result file is simply because your simulation actually didn't run: in the simulation tab, you got an error "Abnormal run completion" which means that an issue has been detected and that the simulation has stopped. Look further into this section to see what the problem is.

Best regards,
Mathieu

Hi BEN,

as you know, the breach is indeed trapezoidal, and the width represents the bottom width.

The breach level describes also the bottom level, so it can be the level you want, except that it doesn't make sense to define a breach level which is below the ground level: so that's a restriction. The initial level is the level describing the bottom of the breach right after the initial failure: you can set this intial breach level equal to the dam level (before failure), if you want to model a smooth / continuous breach development. On the opposite, you may assume that part of the dam is intantaneously destroyed and hence that the breach development is discontinuous: in that case, you can define an initial breach level much lower than the dam level.

Best regards,
Mathieu

Hi Razieh,

if you want to save a time series output, the value in the "Type" column must be 0, and the file extension in the "Data file" column must be *.dfs0. Can you check these two things?

If that looks correct and if the problem persists, you'd better attach your model files, so that someone can have a look and identify the issue.

Best regards,
Mathieu

Dear Helen,

To do that, you can open the first file (file A) in the Grid Editor (simply double-click on the file), and then go to Tools \ Copy file into data...

This will open a new dialog, in which you can select the other file (file B) containing the values to be added.

In the 'Item mapping' options, you can select which item from file B has to be added to each item from file A.

In the 'Operation' options, select '+' to sum the data files.

Best regards,
Mathieu

Hi,

Do you mean that you want to sum the data from different result files?
Or do you simply want to superimpose the maps of results, and e.g. use transparency to visualize the results from different files at the same time?

And do you use the Flexible Mesh version of MIKE 21? Or the rectangular grid one?

Best regards,
Mathieu

Hi Simon,

To model intake structures, you can simply apply one boundary per structure. In the boundary condition file, add a boundary with type "Point source" at each structure's location, and give it a negative discharge (a positive value flows towards the river, and a negative one is "pumped" from the river).

Hope this will help!

Best regards,
Mathieu

Hi,

thank you very much for sharing this with other users!

Best regards,
Mathieu