SimScale CAE Forum

Free surface boundary condition

I am attempting to do a multiphase study that consists of water and air. Instead of using a Geometry Primitive to initialize my water domain I would like to select a volume that is part of my imported model. You can see my setup here:

Tank Level

My issue is the use of 3 volumes, 2 that are Air and 1 that is Water. Where the Air volume meets the Water Volume I would have a free surface. The geometry at this free surface location is made up of 2 faces (one from the Air volume and one from the Water volume). Is there any boundary condition that I can add at this free surface interface that would allow the tank to level itself?

I understand that I could do this with geometry primitives. However, It would be nice to be able to model the Water volume and air volumes in CAD and take care of this interface with a Boundary Condition.


Hi @eweber!

Very nice and interesting project you have there! It might take a while until I can jump onto this but let me tag the PowerUsers @camilomati, @Get_Barried as well as our user @vgon_alves who might help you out with this one in the meantime.



thanks @jousefm
@eweber I recommend working in simscale with a single merged model (not with an assembly or non-merged geometries) for CFD
To give the level you can create two primitive geometries, one for the lowest level (it can be a box) and one smaller box to give the highest level. It does not matter if the boxes intersect or leave the geometry if is the same type of fluid, the important thing is set up a initial condition for the phase fraction of the differents fluids :slight_smile:

look this project
maybe this simulation that I did could guide you on how to configure an initial volume

Thanks for the reply. That was the conclusion I expected. I do understand how I can do it with geometry primitives. I was just hoping that we could do it with the CAD geometry.

Thanks again!

This is probably a better example of why this can be a pain. Here I am trying to do a multiphase simulation of syrup dripping from a nozzle. Notice that I needed to make 23 primitives just so it would not get to the outside of where the nozzle curves because that should be initialize as air.


Bernhard Riemann would be proud of you :vulcan_salute: :mage: