[pipi]

Dear Hans,

Good morning!

I use REEF3D to simulate the dam break process with dry bed and compare the result with Ritter (1982) analytical solution. There are some problems I got.

1. I set the water level at 0.12m, but when I extract data from REEF3D result, the water level has slightly lower than the setting value. And the vertical surface of the dam is slightly inclined. (Figure 1).

2. I already set the slip bed, with no friction, but the result shows the bed is not slipped (Figure 2).

Do you have some suggestions for these?

Kind regards
Dongfang

[valgrinda]

Hi Dongfang,

I suggest the following changes to the setup:

- in the control.txt, C 12 and C13 need to be 3, because you run in 2D and you need symmetry plane boundary conditions there

in the ctrl.txt:
- B 20 2 works better

- N 40 3 (TVD RK3) is much better than N 40 1 (AB 2)

- you can add F 42 1.0 to speed up the initialization process

- N 47 (CFL number) should be fine at 0.1

- there must be a problem in how you extract the data, Paraview shows the free surface to be located at exactly 0.12 m - so everything is ok

[pipi]

Dear Hans,

Appreciate your suggestions!

The N 40 3 (TVD RK3) and N42 1.0 works well!

The reason I set B 20 1 (slip) is that if I set B 20 2 (no-slip bed), the result from REEF3D does not match the Ritters analytical solution very well near the bed. However, even I set slip bed (B 20 1) and no friction, no viscosity, it still shows something resists the water propagates near the bed in REEF3D. The result still cannot create a sharp front as Ritter's analytical solution.

Do you have some ideas for this point?

Thanks in advance.

Kind regards
Dongfang

[valgrinda]

Hi Dongfang,

I think the results look pretty good ! Differences like you show should be acceptable for a numerical model, anything else would be surprising.

[valgrinda]

Hi Dongfang,

sorry for the previous post, I somehow read your figure differently. I think you are still running a 2D simulation with walls in y-direction, see my previous comments. You need to set C 12 and C 13 to 3. Then B 20 2 will be better as well.

Also, I think you are running a domain that is a bit too large for your phenomenon at hand. A tank with smaller length would also do.

[pipi]

Thanks, Hans,

The results are the same as the figures I show before after I change the settings.

But they are already pretty good enough.

Thanks for your help!

Kind regards
Dongfang

[valgrinda]

Hi Dongfang,

could you please upload your most recent control files once more? I am pretty sure that the REEF3D results should be better than depicted in your figure.

[pipi]

Dear Hans,

Thanks!

The attachment is my control files and results (Figure 1).

The initial water level change has been fixed because I use the line probe in the model directly instead of extracting data from Paraview.

Paraview defines the bottom of our model domain at the middle of the bottom cell (Figure 2), which means if we want to use Paraview to read water surface level, we lose half of our mesh-size height, that's the reason why the previous figures show some water level loss (Figure 3).

If you have any suggestions for this case, please contact me, very much appreciate it!

Kind regards
Dongfang