Mathieu Hellegouarch

Hi,

The problem is indeed most likely due to the land values.

When defining an open boundary (on the edges of the domain), there must be land values on the neighboring cells along the edge of the domain.

For internal boundaries, there must be land values on 3 out of the 4 sides of the boundary cell(s).

Does that solve your problem?

Best regards
Mathieu

Hi,

You can also convert the dfs2 file to a *.mesh file, using the MIKE Zero Toolbox called 'File converter \ Mesh converter'.

Once you've loaded this new mesh and the scatter data into the Mesh Generator, you can exporte data to the dfsu file format.

Best regards,
Mathieu

Hi Sophie,

Did you manage to fix your problem?

These two errors are indeed typical errors related to handling of boundaries in MIKE 21. They both happen when a cell from the boundary becomes dry during the simulation.

They can often be avoided by :
- setting a constant topography along the boundaries, on a width of e.g. 3 rows or columns.
- making sure the cells are initially flooded on the same number of rows / columns.

Best regards,
Mathieu

Hi Jérémie,

Indeed there are many constraints which have to be fulfilled when generating a mesh, and especially when dealing with quadrangular meshes.

When using the default 'Algebraic box method', you are not allowed to have more than 4 nodes along the arcs, each of them defining the 4 sides of the quadangular area. So if you have intermediate nodes (instead of vertices), that could be the problem.

Another problem can raise when drawing meanders with high curvature: in that case it may result in some quadrangular elements attempting to cross the meander, outside the quadrangular area, which is not accepted. So you can try to reduce the curvature and see it's better. Alternatively you may try to split a long quandarangular area into smaller areas (by adding arcs to cut the polygon into multiple parts). That may help to avoid odd mesh geometry in meanders.

The "Transfinite interpolation" method wasn't available in older versions of the Mesh Generator, so I suppose you are using one of these versions!

Best regards
Mathieu

Hi,

if you get the message  “The polygon subdivision fail due to the unequal points on both side”, you should try to set the same number of vertices along the polylines on the left and on the right side of the quadrangular area.

Alternatively, you may also try to use the "Transfinite interpolation" method to generate the quadrangular mesh for this polygon: this method is a bit more flexible, and could allow a different number of vertices on both sides.

Regards,
Mathieu

Hi,

this is probably a claccic issue with the classical (rectangular) grid version of MIKE 21: all boundaries must always be wet during the simulation, otherwise boundary conditions aren't applied.

So the issue is most likely that your initial condition is such that the boundary cells are initially dry / inactive, and the result is that the water won't flow from the upstream boundary. The solution is simply to edit the initial condition, and make sure that the boundary cells are initially wet.

Best regards,
Mathieu

Hi Tija,

The reason why it still doesn't work is because the dfs2 file also contains meta-data, which indicate whether the file has a valid format or not for the toolbox. So now that you have removed the extra items from the file, you need to edit the meta data, by following the steps below:

Open a MIKE Zero window and go to File \ Options \ Data Utility. From the new window, open your dfs2 file. Go to the 'Datatype and delete values' menu, and set the data type to 1, and save the file.

Now it should work.

Regards,
Mathieu

Hi Jérémie,

a "Write error" could be due to a lack of free space on your harddisk, or to the fact that you save the result file on a network drive which is unavailable.

To reduce the Courant number, you have to either use coarser cells or reduce the simulation time step. The time step values you mention seem to be quite high, except if you use a very coarse resolution.

Where do you get the Courant number values from? Is this a result, or the informative value which is provided in the 'Simulation period' menu of MIKE 21? Note that the latter is only an approximation, since the actual Courant number will vary during the simulation, depending on water depths and velocities. And do you use a flexible mesh or a rectangular grid?

Best regards,
Mathieu

Hi Jeremie,

I didn't find any clue to explain the problem in your log files.

This isn't a common problem, which probably requires to check the input data. I think you should attach all the setup files, or send them to your local MIKE by DHI support center.

Best regards,
Mathieu

Hi Serafima,

Your guess is correct that it is not possible to directly merge different *.mdf files. However when you've built several polygons, it's quite easy to export them to text files using the menu Data \ Export boundary. You can then import them in another *.mdf file through Data \ Import boundary.
So I suppose this solution may help you.

Regarding your other issue: that looks like a memory issue ! So it can be due either to a big setup, or a low RAM on your computer. If you can't use a computer with bigger RAM, you can try to reduce the number of 'Undo/redo levels' in the Edit \ Options menu. This controls the number of versions of the mesh which are temporary saved in the memory while you edit the mesh, to allow you cancelling the last changes. If you set it to the minimum, you won't be able to undo the last changes, but it will release part of the memory.

Best regards,
Mathieu