Interaction between two fluids

Numerical methods and mathematical models of Elmer
Post Reply
Roy Lampis
Posts: 1
Joined: 25 Oct 2022, 13:42
Antispam: Yes

Interaction between two fluids

Post by Roy Lampis »

Hi everyone, I am entirely new in the FEM world so I am sorry if my questions might sound stupid :| .
I am trying to simulate a flow of water mooving freely in the air to see the interaction between the two fluids.
From what I understood the only way to have two different materials in Elmer is to have two different bodies on which to assign the two different materials, right? So what I did was basically making of a cube of still air with a cylinder of water flowing trough the whole lenght of the cube. I ran the analysis but it gave me some weird results: There were no vectors and no streamlines inside the water cylinder, it looked like if it was completely empty. On the other hand, the flow inside the air box showed some vectors but they were also weird, some vectors attached to the water cylinder were mooving in the opposite direction of the water flow, and overall, I could see some pressure differences but they were in extreme random locations. Apart from that, it lookeed as if it was showing the air particles only, why is that?
And what is the best boundary condition of the surface area between the cylinder and the box? I have used a "free" boundary condition with every velocity unsepecified, so that the water could run out freely. Thank You in advance for the response.
raback
Site Admin
Posts: 4812
Joined: 22 Aug 2009, 11:57
Antispam: Yes
Location: Espoo, Finland
Contact:

Re: Interaction between two fluids

Post by raback »

Hi

If the two flows behave in a sivilized manner and a Lagrangian mesh can be used to follow them (via stretching) the only would my choice be Elmer. Otherwise I would look at OpenFOAM, for example (using FVM). Elmer can do many things but complex multiphase flows is not one of them. Only Eulerian method is somewhat suboptimal levelset. You will find more robust strategies for your problem.

-Peter
Post Reply