# Multiphase Flow Simulation Setting

Good morning everyone, I have some questions about using palabos simulating multiphase multi component fluid. Thank you for your help!

What I’m trying to simulate is in rock pore space, it’s saturated with one fluid and anther fluid will flow through the pore.

I noticed that in example raileighTaylor3D. MultiBlockLattice3D was used, but there is no contact angle or interfacial tension implementation in the examples.
And in examples fallingdroplets, it used TwoPhaseFields3D. it included contact angle or interfacial tension. However Can I still build a bounce back boundary in TwoPhaseFields3D? Sorry my question maybe kind of not smart. But I have been stuck here for a while.

Hi
As far as I know in the raileighTaylor example, the Shan-chen model is used. and there is not any extra force to incorporate the contact angle. So you have to add an extra force on the boundary nodes as it is mentioned in different literatures. For the surface tension, you must be aware of the model you are going to use. Since in the original Shan-Chen model the surface tension is related to the temperature (or Gree,n parameter).
To sum up, you should apply other things to the source code.

Regards

Thank you very much. So field3D is for adding the force field for interfacial tension.
in the example ,there is syntax like this. Do you know what do they do? thank you very much
setToConstant(fields.flag, bottom, (int) twoPhaseFlag::wall);
setToConstant(fields.flag, top, (int) twoPhaseFlag::wall);

I think you are making mistake. Adding an extra force is something else than field3d. 3d refers to 3-dimensional lattice. Generally, adding an extra force needs a descriptor which is present in this example . In the original Shan-Chen model which is used in this example, the surface tension is not adjustable. The only way to adjust the surface tension is changing the G (green function value) which results in changing the density ratio. So As far as I know it is impossible to change surface tension without changing the density ratio.To calculate surface tension in original Shan-Chen model, you need to simulate the Laplace test.

In addition, the following fuctions are somethings which are described in palabos library. Take a look in palabos source codes to find more.
setToConstant(fields.flag, bottom, (int) twoPhaseFlag::wall);
setToConstant(fields.flag, top, (int) twoPhaseFlag::wall);

Regards

Thank you very much. I ended up with editing the fallingDroplet.cpp for simulating my problem.
In:
setToConstant(fields.flag, bottom, (int) twoPhaseFlag::wall);

the bottom is created Cubic. Box3D bottom (0, nx-1, 0, ny-1, 0, 0);

Can I Know if I want to create a Sphere, How can I do it?

I tried to use the way that used in cylinder2d. but it didn’t work.