Multiphase domain needs exactly two materials. Incorrect number of material assignments for the following entities

Using SimScale Fluid Flow / CFD
1

I am getting the below error

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image845×226 7.44 KB

in this project

I want to make a simple multiphase simulation, where I have to chambers with air connected by a pipe with water in it. I assign air to the two top solids and water to the bottom solid. Simscale gives me an error saying I need to assign exactly two materials to the multiphase domain.

What am I doing wrong?

2

Hey there!

I just opened the project and found a different error:

A multi-region mesh was assigned - this analysis-type requires a single-region mesh.

This is because you have three parts in your model.

If what you need is to specify the initial presence of the phases, you should use geometry primitives and initial conditions.

Please elaborate on your model and what you are trying to achieve, so I can give more detailed advice.

1 Like
3

I would like to carry out a very simple simulation where I have different pressures in the two chambers filled with air. The chambers are connected by another chamber filled with water.
I want to see the height of the water change due to the pressures acting on the water surface as seen in the below picture.

https://imgur.com/GoLUotu

I dont understand how to model and mesh this. So far I made the U-shaped body in the project and split it into 3 parts; 2 parts air and 1 part water, is this the wrong approach?

6

Hi, I just created this simulation starting form your model, so you know how it should be done:

Please notice:

  • I fused the three parts in the CAD Edit mode.
  • How I assigned the phase fractions and materials.
  • How I assigned the Initial conditions for the phase fractions, using the geometry primitive.
  • The mesh setup
  • The ramping of the inlet pressure and the boundary conditions in general

You should follow similar guidelines for future multiphase simulations.

7

Hi again, thank you very much for your thorough answer. I still have a of question I hope you could clarify:

You assigned the materials air and water to every part of the solid. I guess that makes sense because every part of the solid can potentially contain water or air? When I originally assigned air to the two top smaller solids and water to the bottom solid, I basically said that air could never leave the small solids and likewise for water?

Thank you

8

You are welcome!

Yes, that is right, just bear in mind that in a multiphase simulation, only one part domain is allowed, thus you need to assign both materials to the one part.

9

Thank you.