SimScale CAE Forum

Help with Modelling Free Surface Water flow

Good morning/afternoon,

I’m trying to simulate flow through a waterway with a series of openings at the bottom. For my project it is important to see how the depth of the water develops overtime, as well as the water velocity through the openings. The waterway is meant to be for fishes to be able to swim upstream when they encounter a small damn or blockage in a river.

After setting everything up, the simulation turns out to be unsuccessful. The error message given is that the calculation time exceeds the maximum. However, before starting the simulation it gives me an estimated calculation time of 35 minutes. I’ve tried increasing the time step and decreasing the simulation time, as well as making the mesh more coarse, but with no luck so far. When I look at the results I notice that nothing is visible when it comes to what had been calculated, it seems as if nothing happened during the calculation. I don’t know whether this is due to something wrong with my parameters or model or with the fact that it is actually very heavy on the system to calculate it, which seems unlikely to me.

I’m wondering if anyone would be so kind to take the time to look at my model and see if there’s anything that can be done to fix this. I sincerely thank you in advance, I’m really enthousiastic about this project and the idea of having a simulation to support my design seems awesome to me.

Here is a link to the project:

Hi Tristan!

Just commenting on your setup now to make sure there’s progress in that regard.

First of all make sure you have a single surface for your whole domain, from what I see this “outer shell” is not really needed. But make sure to close the surface on top as well to make the domain watertight.

Apart from that you can keep the boundary conditions but maybe change the wall on top (that you need to add to make the geometry watertight) to an open surface (pressure outlet BC) and you can keep the velocity inlet as it is.

As you have seen from your messages during the run, you also have to make sure that your CFL condition is not violated, more information about that can be found here:

Hope that small input helped you, for any other questions always feel free to tag the @CFD-SQUAD.



Thanks so much! I will let you know if it works!

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I have now tried what you suggested, the only problem now is that it gives me an error that a setup with 25 regions is being used in a single-region analysis type. I’m not exactly sure what this means unfortunately so I’m a bit confused, I have assigned the faces to only one volume . Would you mind taking a look at it? I have made a new project with the following link: (or anybody willing to take a look @CFD-SQUAD)

Nevermind, I figured out that model is seen as 25 different volumes, I made a simple version of the design to see if that works: . I’ll see if this gives any results @CFD-SQUAD @jousefm

Even with this simple version I don’t seem to get any results, I feel stuck and this program seems to be more difficult than I originally anticipated. I would appreciate any help possible! For anyone willing to help take a look at the project below: