## Fluids

#### If a liquid is used to replace another liquid, which model is suitable?

• h395523899
Subscriber

There is oil in the pipeline, and water is used to replace it. Which model is suitable?

Euler or vof?

• raul.raghav
Subscriber

You need to provide a schematic of your setup so we can suggest you the best approach. But two incompressible, immiscible fluids - VOF should work fine if the conditions are favorable - like a simple stratified flow morphology (an interface that's simple enough to be tracked, no complex regions in the pipeline geometry etc).

• Raef.Kobeissi
Subscriber

I agree with Rahul, If you are interested in the interface between the 2 fluids you may have to use the volume of fluid model (VOF).

Example:

• h395523899
Subscriber

First of all, thank you for your help.

1. I want to simulate the water level for the top of the oil to understand the remaining condition of the oil in the channel. The initial conditions in the model are all oil, water comes in from the entrance. This situation does not know whether to use Euler or vof.

2. I have drawn the model into three parts. The main part is a thin plate-shaped channel, and the second part is a semi-circular cavity communicating with the thin plate, which is located at the middle of one side of the thin plate. The third part is porous media, located on the semi-circular cavity side of the sheet. The boundary conditions I use are as follows: Euler's theorem, turbulent k-e equations, inlet velocity 2 m/s, free exit. The three parts are connected via interface.

3, I encountered the problem is: the same boundary conditions, I use the thin channel simulation, it can smoothly iterate. At the same time, I connected the thin-walled channel only to the porous media and it also smoothly passed through it. When I connect the sheet channel with the semi-circular cavity, or when the three parts are connected together, the iteration is always divergent.

• h395523899
Subscriber

I can't see the picture you sent. Can I send it again? Thank you

• h395523899
Subscriber

I don't know if this divergence has anything to do with the number of meshes in my model.

My model is 20m long, 10m wide, the thickness of the thin plate channel is 10mm, and the radius of the hemispherical cavity is 3m.

Mesh painted with icem. Structure grid is about 80,000. It is then converted to an unstructured grid. The quality of the grid can also be.