[natt polcar]

hello i'm trying to model multiphase open channel flow with a side weir.

I need to match experimental conditions of Froude number and flow depth at a location just before the side weir in order to compare results with experimental results.

so I modeled with velocity and flow depth that matches these two values at the inlet(which is 2m away form opening of weir) but I observe that water level just before the weir is much lower than inlet value(which is the value required) for steady state solution.

is there any way of matching depth and froude number of simulation and experiment?

[marmot]

I assume you are using VOF, here are some questions I would ask myself,

-Is the grid fine enough to resolve the air/water interface?
-Is my fluid domain large enough, do I have enough cells far enough away from the water surface so my boundary conditions are not affecting anything?
-Is the mass of water constant in my domain (inlet to outlet) sometimes with VOF you have smearing and you can loose water.
-Is surface tension on?
-Is the VOF sharpening factor on, numerical trick to keep a sharp interface but can result in unphysical results.
-Is gravity model turned on, is it pointing in the right direction.

Sounds like a fun problem, enjoy

[natt polcar]

Thanks a lot for the reply.

I checked for the mass flow rates and ensured no loss, the surface tension phase interaction option was on.
I was able to get a much sharper interface with your advice using a VOF sharpening factor of 0.3.

The problem I'm facing is that the water surface level (which I need to maintain up to the upstream region of the side weir) suddenly reduces close to the inlet itself, like something resembling a hydraulic drop.

I'm modeling subcritical flow and have set the entire outlet boundary as a pressure outlet. How to maintain water surface level up to the weir ?Should I be using some downstream control mechanism(like a control gate)?