User Forum of Software BASEMENT

rycandra

User

Registered: 2014-09-11

Posts: 2

mass balance in the output file

Hallo all,

I'm simulating now the reservoir sedimentation and interested in the amount of sediment trapped in the reservoir. The reservoir serves as hydropower and irrigation reservoir. The run time simulation is 24 hours. I use the special output type "balance" with the value of "sediment" to get the information about the mass conservation of the sediment. For information, I removed the soil layer in order to make it as fix soil to avoid the erosion in the reservoir. Also, the initial condition of suspended load is set to clear water. Therefore I don't have initial volume of sediment and suspension as well in the reservoir. The problem is the result of the simulation shows that the sediment outflow (both bedload and suspended load) and the sediment trapped in the reservoir are much more bigger than the inflow(which is impossible), as shown as follows:

bedload boundary inflow = 3217.25 m³; bedload boundary outflow = 715065.414 m³
suspension boundary inflow = 12806.493 m³; suspension boundary outflow = 1660535.12 m³
present sediment volume = 25209438.9 m³
present suspension volume = 4455730650 m³

I also couldn't find the relation of the values from one to another columns in the table. It seems that a value in a column doesn't influence another value in such a column.
Maybe someone can explain? Thanks in advance.

Regards,

Gerry

ps. follow this link to see the balance output file:
https://www.dropbox.com/s/euvyx2rul49ik … .xlsx?dl=0

Last edited by rycandra (2014-09-24 10:56:36)

Christian Volz

User

Registered: 2014-09-04

Posts: 31

Re: mass balance in the output file

Dear Gerry

taking a look at your balance file, there is obviously something wrong with the overall sediment balance. There were some known issues with the sediment balance and fixed beds in the past. We had thought these problems were corrected, but perhaps there is still an issue left. In most models either bed-load or suspended-load is simulated, the combination of both transport processes is not very common and may also be a possible cause for the problem here.

To locate and isolate the problem it would be helpful to try e.g. some of the following measures and to check if the problem with the sediment balance persists:

- Activate only one type of transport, either bed- or suspended-load.
- Replace the fixed bed with a movable bed.
- If you have activated the "morph-cycle",  de-activate this option.
- Try to simplify the model, e.g. by simulating only a part of the mesh. This may help to see if the problem is related to very distorted cells in the mesh.
- If you have distorted cells in the mesh, you may also want to try to generate a mesh with smooth transition zones and without geometrical problematic cells.

This should help to narrow down the problem. With more detailed information and, if possible, a simplified model, we hopefully are able to fix the problem.

Regards,
Christian