User Forum of Software BASEMENT

Debora

User

Registered: 2024-10-18

Posts: 2

High velocities at the inlet section

Hi everyone,
I’m trying to implement the initial conditions for a hydraulic model with sediment transport, but I’m encountering an issue.

In the first cells of the domain, I’m getting very high velocities, while immediately downstream the velocity stabilizes toward expected values. The channel bed has a slope of 0.24%, and I set the initial discharge to 30 m³/s constant (the flood hydrograph reaches about 900 m³/s at peak).

I’m wondering if this might be a numerical issue. I’ve attached the input files for reference:
https://u.pcloud.link/publink/show?code … wSXuM1QmL7

Any advice or suggestions would be greatly appreciated.
Thank you!

Lukas Vonwiller

Developer

Registered: 2014-09-04

Posts: 157

Re: High velocities at the inlet section

Hi Debora

Maybe you could try to use "froude_in" type boundary at the inflow. Thereby you can define a froude number, e.g. for sub-critical flow.

Hope this helps!

Br, Lukas

Debora

User

Registered: 2024-10-18

Posts: 2

Re: High velocities at the inlet section

Thank you, Lukas, your suggestion worked!

However, while running some tests and looking at the influence of the initial conditions, I noticed that if I increase the slope, at the same flow rate, the issue of high inlet velocities is progressively reduced.
That said, this solution is not very realistic in practice. Do you have any other ideas or suggestions?

However, when I try to run the flood hydrograph, everything works correctly up to a certain point (around 16,800 s out of a total of 60,000 s), where there is a sudden increase in the inflow velocities (from 4 m/s to 8–10 m/s), and I don’t understand why. Could this be a problem related to the morphology of the inlet section?

Thank you for your help.
Debora

Last edited by Debora (2025-12-19 16:01:08)