Mathieu Hellegouarch

Hi,

Regarding case 1 : the way you proceeded seems to be correct.
For question 1: there is no numerical limit for the length of link channel
Q2: I'm not sure what you refer to when you mention the link channel geometry. If you refer to the bank / spilling elevation: this is specified in the 'Cross section geometry' options, and describes the geometry of a weir describing the bank.
Q3: Yes you should define multiple link channels: that will allow for a better description of the spilling level along the river branch, and will also allow taking into account the water level changes along the river. You could use MIKE FLOOD instead, which will be usually better because it may use a fully 2D approach for the floodplain. Using MIKE FLOOD is also sometimes even easier than setting up a high number of link channels.
Q4: when applying a storage on a link channel: you have to add a cross-section at the location of the storage (upstream or downstream end of the link channel) and define the Level / Storage area in the processed data of this cross-section (by use of teh Additional Storage Area column). If you use the link channel to model the spilling over a single location, into a reservoir, it may be easier to use a side structure (weir type) with reservoir, which is easier to set up.

Case 2: using a side structure or a link channel is basically the same, except that when using a weir you can select which weir formula you want to use. And when using a side structure weir, the Plot button can only display the upstream and downstream cross-sections, even for a side structure!
The end chainage for a side struture will allows use a default value, so it's not based on the geometry.

Best regards,
Mathieu

Hi Aileen,

A source is actually defined with a discharge value ! You're probably using the classical version of MIKE 21 (using a rectangular grid), and in this version the discharge is specified in the 'Magnitude' field, or through an external time series.

The 'Velocity' field is an additional parameters which indicates the initial current speed of the source, but which doesn't replace the discharge value.

Best regards,
Mathieu

Hi,
Here is some information regarding your questions:
1. You can very easily apply marks in all cross-sections: mark 1 represents the left end of the active area, and mark 3 the right end of this area. So, the parts of the cross-section which are located to the left of mark 1 or the right of mark 3 are not used in the simulation (just like if there were very high vertical walls above these marks. This is very convenient if you need to exclude a part of a cross-section when you know it won't be flooded.

In case this side part of the cross-section is to be flooded at some point in time during the simulation (e.g. a storage area during a flood event), you therefore need to describe this additional area with another calculation point. You can for example use a link channel (describing an overbank spilling) with the storage area located downstream this link, or you can use a second branch to model the flow through the side part of the cross-section (this second solution is relevant if you need to model parallel flows, e.g. in the main riverbed and in the floodplain). In both options, you get two different calculation points for the same cross-section, which will give you different levels in the main part of the cross-section and in the side part.

2. I suppose the number of iterations you're looking for is the parameter 'NoIter', available in the 'Default values' tab in the *.hd11 file. The default value of 1, which means that MIKE 11 performs 1 additional iteration after the default calculation (or 1st iteration), is usually suitable.

3. There is no easy way to remove all interpolated cross-sections at the same time. If you have much more interpolated cross-sections than 'real' surveyed sections, you can consider doing the following: select the cross-sections you want to keep, export them to a text file (File > Export), delete the whole river branch, import the saved cross-sections (File > Import) again.
If you simply added the interpolated cross-sections to get a finer resolution (with additional computational points), you can simply use the 'Maximum dx' parameter instead. This parameter is defined in the branch properties, and defines the maximum distance between calculation points for each branch. The necessary additional computational points are added at run time only, and hence it is extremely easy to revert back to a coarser resolution if needed.

I hope this is clear, otherwise just let us know.

Best regards
Mathieu

Hi Vic,

the reason for that if probably because you are currently in "Arc editing" mode, whereas you should change this to "Mesh editing" mode (you can't edit both at the same time). This can be selected in the 'Mesh' menu.

Best regards,
Mathieu

Hi Aileen,

The reason why you don't see this blow-up in the results is probably because you don't save the results for each simulated time step: the last saved time step in the result file may therefore be far earlier than the blow-up.

A blow-up is related to an instability, and instabilities often occur at places where high velocities occur: so it is often due to velocities more than water depths, and it's hence not surprising that yours is detected at a location with low water depth.

The first thing to check is that you use an appropriate simulation time step. This time step usually needs to be such that the Courant number remains lower than 1. If you're working on flood applications, this results in a time step which is usually lower or equal to the cell size divided by a factor 5. I suggest that you check if this is a case in your model, and reduce the time step if necessary.

If the instability occurs close to a boundary, the problem may also be fixed by smoothing the bathymetry along the boundaries.

I hope these tips can help. Your issue may however be due to something different but it's difficult to give more advices without additional description of the model. So don't hesitate to give more details if that doesn't help.

Best regards,
Mathieu

Hi Pamenifor,

Yes, this is possible. After clicking the 'Select gridpoint' icon in the toolbar, you can click 'List' to get access to the full list of calculation points. From here, you can select a number of calculation points, and then click 'Show values' to get the results in a table format.

Best regards
Mathieu

Hi Olkeba,

I can't figure out what can cause this error. I think you should contact your official support center for additional help (see e-mail adress here: http://www.mikebydhi.com/Support/DHISupportCentres.aspx). You should also attach your model files to the e-mail in order for DHI to reproduce and analyze the issue.

Best regards,
Mathieu

Hi,

Did you check the log file created by MIKE 11 during the initialization? It may contain a description of the problem.

This file is located in the folder containing the MIKE 11 setup files, and has the the same name as the *.sim11 file but with the *.log file extension.

Best regards,
Mathieu

Hi Pamenifor,

It is not possible to edit a number of boundaries at the same time.

I'm not sure whether you use constant values or time series (external files) to define the flow values, but in case you use external time series, and if you simply need to change the name of the time series for each boundary, you may change this by editing the *.bnd11 file in a text editor (like NotePad), in which you can use the "Search and replace" option to search for the name of the previous time series and change it to the new one.

Hope this information may help.

Best regards,
Mathieu

Hi Pamenifor,

you usually don't need this information when you import new cross-sections. You can indeed import only the geometry of the cross-sections by keeping the defaultt settings for the Processed Data.

Once the cross-sections are imported, you can easily change (if needed) the way the processed data are calculated from the Grapichal interface: this is usually easier to do from the interface than in the text file.

Best regards,
Mathieu